Dubowitz syndrome (DS) is a rare multiple congenital syndrome characterized primarly by growth retardation, microcephaly, distinctive facial dysmorphism, cutaneous eczema, a mild to severe intellectual deficit and genital abnormalities.

Johanson-Blizzard syndrome is an autosomal recessive disorder characterized by poor growth, mental retardation, and variable dysmorphic features, including aplasia or hypoplasia of the nasal alae, abnormal hair patterns or scalp defects, and oligodontia. Other features include hypothyroidism, sensorineural hearing loss, imperforate anus, and pancreatic exocrine insufficiency (summary by Al-Dosari et al., 2008).

Aarskog-Scott syndrome is a genetic disorder that affects the development of many parts of the body, most commonly the head and face, the hands and feet, and the genitals and urinary system (genitourinary tract). This condition mainly affects males, although females may have mild features of the syndrome.\n\nPeople with Aarskog-Scott syndrome often have distinctive facial features, such as widely spaced eyes (hypertelorism), a small nose, a long area between the nose and mouth (philtrum), and a widow's peak hairline. They frequently have mild to moderate short stature during childhood, but their growth usually catches up with that of their peers during puberty. Hand abnormalities are common in this syndrome and include short fingers (brachydactyly), curved pinky fingers (fifth finger clinodactyly), webbing of the skin between some fingers (cutaneous syndactyly), and a single crease across the palm. Affected individuals can also have wide, flat feet with broad, rounded toes. Other abnormalities in people with Aarskog-Scott syndrome include heart defects and a split in the upper lip (cleft lip) with or without an opening in the roof of the mouth (cleft palate).\n\nMost males with Aarskog-Scott syndrome have a shawl scrotum, in which the scrotum surrounds the penis instead of hanging below. Less often, they have undescended testes (cryptorchidism) or a soft out-pouching around the belly-button (umbilical hernia) or in the lower abdomen (inguinal hernia).\n\nThe intellectual development of people with Aarskog-Scott syndrome varies widely. Most individuals with Aarskog-Scott syndrome have normal intelligence; however, some may have mild learning and behavior problems, and in rare cases, severe intellectual disability has been reported.

KBG syndrome is typically characterized by macrodontia (especially of the upper central incisors), characteristic facial features (triangular face, brachycephaly, synophrys, widely spaced eyes, broad or bushy eyebrows, prominent ears, prominent nasal bridge, bulbous nose, anteverted nares, long philtrum, and thin vermilion of the upper lip), short stature, developmental delay / intellectual disability, and behavioral issues. Affected individuals may have feeding difficulties (particularly in infancy), skeletal anomalies (brachydactyly, large anterior fontanelle with delayed closure, scoliosis), hearing loss (conductive, mixed, and sensorineural), seizure disorder, and brain malformations. There is significant variability in the clinical findings, even between affected members of the same family.

A type of hypothyroidism that results from a defect in thyrotropin-releasing hormone activity.

Coffin-Lowry syndrome (CLS) is usually characterized by severe-to-profound intellectual disability in males; less severely impaired individuals have been reported. Neuropsychiatric concerns can include behavioral problems, loss of strength, progressive spasticity or paraplegia, sleep apnea, or stroke. Stimulus-induced drop attacks (SIDAs) in which unexpected tactile or auditory stimuli or excitement triggers a brief collapse but no loss of consciousness are present in approximately 20% of affected individuals. Typically SIDAs begin between mid-childhood and the teens. Characteristic facial features may be more apparent with age. Upper-extremity differences may be subtle and include short, soft, fleshy hands with tapered fingers as well as fleshy forearms. Progressive kyphoscoliosis is one of the most difficult aspects of long-term care. Affected females tend to have intellectual disability in the mild-to-moderate range and may also have the typical facial, hand, and skeletal findings noted in males.

The autosomal dominant TRPV4 disorders (previously considered to be clinically distinct phenotypes before their molecular basis was discovered) are now grouped into neuromuscular disorders and skeletal dysplasias; however, the overlap within each group is considerable. Affected individuals typically have either neuromuscular or skeletal manifestations alone, and in only rare instances an overlap syndrome has been reported. The three autosomal dominant neuromuscular disorders (mildest to most severe) are: Charcot-Marie-Tooth disease type 2C. Scapuloperoneal spinal muscular atrophy. Congenital distal spinal muscular atrophy. The autosomal dominant neuromuscular disorders are characterized by a congenital-onset, static, or later-onset progressive peripheral neuropathy with variable combinations of laryngeal dysfunction (i.e., vocal fold paresis), respiratory dysfunction, and joint contractures. The six autosomal dominant skeletal dysplasias (mildest to most severe) are: Familial digital arthropathy-brachydactyly. Autosomal dominant brachyolmia. Spondylometaphyseal dysplasia, Kozlowski type. Spondyloepiphyseal dysplasia, Maroteaux type. Parastremmatic dysplasia. Metatropic dysplasia. The skeletal dysplasia is characterized by brachydactyly (in all 6); the five that are more severe have short stature that varies from mild to severe with progressive spinal deformity and involvement of the long bones and pelvis. In the mildest of the autosomal dominant TRPV4 disorders life span is normal; in the most severe it is shortened. Bilateral progressive sensorineural hearing loss (SNHL) can occur with both autosomal dominant neuromuscular disorders and skeletal dysplasias.

The autosomal dominant TRPV4 disorders (previously considered to be clinically distinct phenotypes before their molecular basis was discovered) are now grouped into neuromuscular disorders and skeletal dysplasias; however, the overlap within each group is considerable. Affected individuals typically have either neuromuscular or skeletal manifestations alone, and in only rare instances an overlap syndrome has been reported. The three autosomal dominant neuromuscular disorders (mildest to most severe) are: Charcot-Marie-Tooth disease type 2C. Scapuloperoneal spinal muscular atrophy. Congenital distal spinal muscular atrophy. The autosomal dominant neuromuscular disorders are characterized by a congenital-onset, static, or later-onset progressive peripheral neuropathy with variable combinations of laryngeal dysfunction (i.e., vocal fold paresis), respiratory dysfunction, and joint contractures. The six autosomal dominant skeletal dysplasias (mildest to most severe) are: Familial digital arthropathy-brachydactyly. Autosomal dominant brachyolmia. Spondylometaphyseal dysplasia, Kozlowski type. Spondyloepiphyseal dysplasia, Maroteaux type. Parastremmatic dysplasia. Metatropic dysplasia. The skeletal dysplasia is characterized by brachydactyly (in all 6); the five that are more severe have short stature that varies from mild to severe with progressive spinal deformity and involvement of the long bones and pelvis. In the mildest of the autosomal dominant TRPV4 disorders life span is normal; in the most severe it is shortened. Bilateral progressive sensorineural hearing loss (SNHL) can occur with both autosomal dominant neuromuscular disorders and skeletal dysplasias.

Acromicric dysplasia (ACMICD) is an autosomal dominant disorder characterized by severe short stature, short hands and feet, joint limitations, and skin thickening. Radiologic features include delayed bone age, cone-shaped epiphyses, shortened long tubular bones, and ovoid vertebral bodies. Affected individuals have distinct facial features, including round face, well-defined eyebrows, long eyelashes, bulbous nose with anteverted nostrils, long and prominent philtrum, and thick lips with a small mouth. Other characteristic features include hoarse voice and pseudomuscular build, and there are distinct skeletal features as well, including an internal notch of the femoral head, internal notch of the second metacarpal, and external notch of the fifth metacarpal (summary by Le Goff et al., 2011). Allelic disorders with overlapping skeletal and joint features include geleophysic dysplasia-2 (GPHYSD2; 614185) and the autosomal dominant form of Weill-Marchesani syndrome (608328).

INSR-related severe syndromic insulin resistance comprises a phenotypic spectrum that is a continuum from the severe phenotype Donohue syndrome (DS) (also known as leprechaunism) to the milder phenotype Rabson-Mendenhall syndrome (RMS). DS at the severe end of the spectrum is characterized by severe insulin resistance (hyperinsulinemia with associated fasting hypoglycemia and postprandial hyperglycemia), severe prenatal growth restriction and postnatal growth failure, hypotonia and developmental delay, characteristic facies, and organomegaly involving heart, kidneys, liver, spleen, and ovaries. Death usually occurs before age one year. RMS at the milder end of the spectrum is characterized by severe insulin resistance that, although not as severe as that of DS, is nonetheless accompanied by fluctuations in blood glucose levels, diabetic ketoacidosis, and – in the second decade – microvascular complications. Findings can range from severe growth delay and intellectual disability to normal growth and development. Facial features can be milder than those of DS. Complications of longstanding hyperglycemia are the most common cause of death. While death usually occurs in the second decade, some affected individuals live longer.

Aspartylglucosaminuria (AGU) is a severe autosomal recessive lysosomal storage disorder that involves the central nervous system and causes skeletal abnormalities as well as connective tissue lesions. The most characteristic feature is progressive mental retardation. The disorder is caused by deficient activity of the lysosomal enzyme glycosylasparaginase, which results in body fluid and tissue accumulation of a series of glycoasparagines, i.e., glycoconjugates with an aspartylglucosamine moiety at the reducing end. AGU belongs to the group of disorders commonly referred to as the Finnish disease heritage (summary by Mononen et al., 1993 and Arvio and Arvio, 2002).

Lysinuric protein intolerance (LPI) typically presents after an infant is weaned from breast milk or formula; variable findings include recurrent vomiting and episodes of diarrhea, episodes of stupor and coma after a protein-rich meal, poor feeding, aversion to protein-rich food, failure to thrive, hepatosplenomegaly, and muscular hypotonia. Over time, findings include: poor growth, osteoporosis, involvement of the lungs (progressive interstitial changes, pulmonary alveolar proteinosis) and of the kidneys (progressive glomerular and proximal tubular disease), hematologic abnormalities (normochromic or hypochromic anemia, leukopenia, thrombocytopenia, erythroblastophagocytosis in the bone marrow aspirate), and a clinical presentation resembling the hemophagocytic lymphohistiocytosis/macrophagic activation syndrome. Hypercholesterolemia, hypertriglyceridemia, and acute pancreatitis can also be seen.

Laron syndrome is an autosomal recessive disorder characterized by marked short stature that results from failure to generate insulin-like growth factor I (IGF1; 147440) in response to growth hormone (GH; 139250). GH levels are normal or increased. The disorder is caused by dysfunction of the growth hormone receptor. A Laron syndrome-like phenotype associated with immunodeficiency (245590) is caused by a postreceptor defect, i.e., mutation in the STAT5B gene (604260). Patients with mutations in the GHR gene that cause only partial insensitivity to growth hormone have a form of short stature (604271).

D-bifunctional protein deficiency is a disorder of peroxisomal fatty acid beta-oxidation. See also peroxisomal acyl-CoA oxidase deficiency (264470), caused by mutation in the ACOX1 gene (609751) on chromosome 17q25. The clinical manifestations of these 2 deficiencies are similar to those of disorders of peroxisomal assembly, including X-linked adrenoleukodystrophy (ALD; 300100), Zellweger cerebrohepatorenal syndrome (see 214100) and neonatal adrenoleukodystrophy (NALD; see 601539) (Watkins et al., 1995). DBP deficiency has been classified into 3 subtypes depending upon the deficient enzyme activity. Type I is a deficiency of both 2-enoyl-CoA hydratase and 3-hydroxyacyl-CoA dehydrogenase; type II is a deficiency of hydratase activity alone; and type III is a deficiency of dehydrogenase activity alone. Virtually all patients with types I, II, and III have a severe phenotype characterized by infantile-onset of hypotonia, seizures, and abnormal facial features, and most die before age 2 years. McMillan et al. (2012) proposed a type IV deficiency on the basis of less severe features; these patients have a phenotype reminiscent of Perrault syndrome (PRLTS1; 233400). Pierce et al. (2010) noted that Perrault syndrome and DBP deficiency overlap clinically and suggested that DBP deficiency may be underdiagnosed.

GAPO syndrome is the acronymic designation for a complex of growth retardation, alopecia, pseudoanodontia (failure of tooth eruption), and progressive optic atrophy (Tipton and Gorlin, 1984). Ilker et al. (1999) and Bayram et al. (2014) noted that optic atrophy is not a consistent feature of the disorder.

Trichorhinophalangeal syndrome (TRPS) comprises TRPS I (caused by a heterozygous pathogenic variant in TRPS1) and TRPS II (caused by contiguous gene deletion of TRPS1, RAD21, and EXT1). Both types of TRPS are characterized by distinctive facial features; ectodermal features (fine, sparse, depigmented, and slow growing hair; dystrophic nails; and small breasts); and skeletal findings (short stature; short feet; brachydactyly with ulnar or radial deviation of the fingers; and early, marked hip dysplasia). TRPS II is characterized by multiple osteochondromas (typically first observed clinically on the scapulae and around the elbows and knees between ages 1 month and 6 years) and an increased risk of mild-to-moderate intellectual disability.

Microcephalic osteodysplastic primordial dwarfism type II (MOPDII), the most common form of microcephalic primordial dwarfism, is characterized by extreme short stature and microcephaly along with distinctive facial features. Associated features that differentiate it from other forms of primordial dwarfism and that may necessitate treatment include: abnormal dentition, a slender bone skeletal dysplasia with hip deformity and/or scoliosis, insulin resistance / diabetes mellitus, chronic kidney disease, cardiac malformations, and global vascular disease. The latter includes neurovascular disease such as moyamoya vasculopathy and intracranial aneurysms (which can lead to strokes), coronary artery disease (which can lead to premature myocardial infarctions), and renal vascular disease. Hypertension, which is also common, can have multiple underlying causes given the complex comorbidities.

Lenz-Majewski hyperostotic dwarfism is a rare condition characterized by intellectual disability, sclerosing bone dysplasia, distinct craniofacial and dental anomalies, loose skin, and distal limb anomalies, particularly brachydactyly and symphalangism. Patients have multiple radiographic abnormalities due to progressive generalized hyperostosis that affects the cranium, vertebrae, and diaphyses of tubular bones, leading to severe growth retardation (summary by Sousa et al., 2014).

IGHD3 is characterized by agammaglobulinemia and markedly reduced numbers of B cells, short stature, delayed bone age, and good response to treatment with growth hormone (summary by Conley et al., 1991). For general phenotypic information and a discussion of genetic heterogeneity of IGHD, see 262400.

Floating-Harbor syndrome (FHS) is characterized by typical craniofacial features; low birth weight, normal head circumference, and short stature; bone age delay that normalizes between ages six and 12 years; skeletal anomalies (brachydactyly, clubbing, clinodactyly, short thumbs, prominent joints, clavicular abnormalities); severe receptive and expressive language impairment; hypernasality and high-pitched voice; and intellectual disability that is typically mild to moderate. Difficulties with temperament and behavior that are present in many children tend to improve in adulthood. Other features can include hyperopia and/or strabismus, conductive hearing loss, seizures, gastroesophageal reflux, renal anomalies (e.g., hydronephrosis / renal pelviectasis, cysts, and/or agenesis), and genital anomalies (e.g., hypospadias and/or undescended testes).

Cantú syndrome is characterized by congenital hypertrichosis; distinctive coarse facial features (including broad nasal bridge, wide mouth with full lips and macroglossia); enlarged heart with enhanced systolic function or pericardial effusion and in many, a large patent ductus arteriosus (PDA) requiring repair; and skeletal abnormalities (thickening of the calvaria, broad ribs, scoliosis, and flaring of the metaphyses). Other cardiovascular abnormalities may include dilated aortic root and ascending aorta with rare aortic aneurysm, tortuous vascularity involving brain and retinal vasculature, and pulmonary arteriovenous communications. Generalized edema (which may be present at birth) spontaneously resolves; peripheral edema of the lower extremities (and sometimes arms and hands) may develop at adolescence. Developmental delays are common, but intellect is typically normal; behavioral problems can include attention-deficit/hyperactivity disorder, autism spectrum disorder, obsessive-compulsive disorder, anxiety, and depression.

Moderate to severe intellectual deficit, seizures, short stature, and skeletal dysplasia. Other manifestations can be associated (retinal abnormalities, brachydactyly, prognathism, dental malocclusion). It is transmitted as an autosomal recessive trait.

Myhre syndrome is a connective tissue disorder with multisystem involvement, progressive and proliferative fibrosis that may occur spontaneously or following trauma or surgery, mild-to-moderate intellectual disability, and in some instances, autistic-like behaviors. Organ systems primarily involved include: cardiovascular (congenital heart defects, long- and short-segment stenosis of the aorta and peripheral arteries, pericardial effusion, constrictive pericarditis, restrictive cardiomyopathy, and hypertension); respiratory (choanal stenosis, laryngotracheal narrowing, obstructive airway disease, or restrictive pulmonary disease), gastrointestinal (pyloric stenosis, duodenal strictures, severe constipation); and skin (thickened particularly on the hands and extensor surfaces). Additional findings include distinctive craniofacial features and skeletal involvement (intrauterine growth restriction, short stature, limited joint range of motion). To date, 55 individuals with molecularly confirmed Myhre syndrome have been reported.

The C syndrome, also known as Opitz trigonocephaly syndrome, is a malformation syndrome characterized by trigonocephaly, severe mental retardation, hypotonia, variable cardiac defects, redundant skin, and dysmorphic facial features, including upslanted palpebral fissures, epicanthal folds, depressed nasal bridge, and low-set, posteriorly rotated ears (summary by Kaname et al., 2007). C syndrome shows phenotypic overlap with Bohring-Opitz syndrome, or C-like syndrome (605039), a disorder with more severe features than C syndrome, caused by heterozygous mutation in the ASXL1 gene (612990) on chromosome 20q11.

SHORT syndrome is a mnemonic for short stature, hyperextensibility, ocular depression (deeply set eyes), Rieger anomaly, and teething delay. It is now recognized that the features most consistently observed in SHORT syndrome are mild intrauterine growth restriction (IUGR); mild to moderate short stature; partial lipodystrophy (evident in the face, and later in the chest and upper extremities, often sparing the buttocks and legs); and a characteristic facial gestalt. Insulin resistance may be evident in mid-childhood or adolescence, although diabetes mellitus typically does not develop until early adulthood. Other frequent features include Axenfeld-Rieger anomaly or related ocular anterior chamber dysgenesis, delayed dentition and other dental issues, and sensorineural hearing loss.

Cardiofaciocutaneous (CFC) syndrome is characterized by cardiac abnormalities (pulmonic stenosis and other valve dysplasias, septal defects, hypertrophic cardiomyopathy, rhythm disturbances), distinctive craniofacial appearance, and cutaneous abnormalities (including xerosis, hyperkeratosis, ichthyosis, keratosis pilaris, ulerythema ophryogenes, eczema, pigmented moles, hemangiomas, and palmoplantar hyperkeratosis). The hair is typically sparse, curly, fine or thick, woolly or brittle; eyelashes and eyebrows may be absent or sparse. Nails may be dystrophic or fast growing. Some form of neurologic and/or cognitive delay (ranging from mild to severe) is seen in all affected individuals. Neoplasia, mostly acute lymphoblastic leukemia, has been reported in some individuals.

Sponastrime dysplasia is an autosomal recessive spondyloepimetaphyseal dysplasia (SEMD) named for characteristic clinical and radiographic findings, including spine (spondylar) abnormalities, midface hypoplasia with a depressed nasal bridge, and striation of the metaphyses. Additional features include disproportionate short stature with exaggerated lumbar lordosis, scoliosis, coxa vara, limited elbow extension, small dysplastic epiphyses, childhood cataracts, short dental roots, and hypogammaglobulinemia. Radiographically, the abnormalities of the lumbar vertebral bodies are suggested to be the most specific finding because the characteristic metaphyseal striations may not be apparent at young ages. Striking clinical variability in presentation, severity, and associated features has been observed (summary by Burrage et al., 2019).

Nicolaides-Baraitser syndrome (NCBRS) is characterized by sparse scalp hair, prominence of the inter-phalangeal joints and distal phalanges due to decreased subcutaneous fat, characteristic coarse facial features, microcephaly, seizures, and developmental delay / intellectual disability. Seizures are of various types and can be difficult to manage. Developmental delay / intellectual disability (ID) is severe in nearly a half, moderate in a third, and mild in the remainder. Nearly a third never develop speech or language skills.

Legg-Calve-Perthes disease (LCPD) is characterized by loss of circulation to the femoral head, resulting in avascular necrosis in a growing child. Clinical pictures of the disease vary, depending on the phase of disease progression through ischemia, revascularization, fracture and collapse, and repair and remodeling of the bone. The disease occurs more frequently in boys, and most patients tend to be shorter than their peers. Both familial and isolated cases of LCPD have been reported (summary by Chen et al., 2004).

Andersen-Tawil syndrome (ATS) is characterized by a triad of: episodic flaccid muscle weakness (i.e., periodic paralysis); ventricular arrhythmias and prolonged QT interval; and anomalies including low-set ears, widely spaced eyes, small mandible, fifth-digit clinodactyly, syndactyly, short stature, and scoliosis. Affected individuals present in the first or second decade with either cardiac symptoms (palpitations and/or syncope) or weakness that occurs spontaneously following prolonged rest or following rest after exertion. Mild permanent weakness is common. Mild learning difficulties and a distinct neurocognitive phenotype (i.e., deficits in executive function and abstract reasoning) have been described.

A rare multiple congenital anomalies/dysmorphic syndrome characterized by global developmental delay, intellectual disability, hypotonia, seizures, microcephaly, delayed bone maturation, and skeletal abnormalities (such as scoliosis or pectus excavatum, among others). Dysmorphic features include coarse face, hirsutism, thick eyebrows, broad nasal septum, short philtrum, large mouth, and prominent ears. There have been no further descriptions in the literature since 1996.

Dental anomalies and short stature (DASS) is characterized by significant short stature with brachyolmia as well as hypoplastic amelogenesis imperfecta with almost absent enamel (Huckert et al., 2015). Some patients exhibit valvular and/or vascular defects, including mitral valve prolapse, aortic root dilation, and aortic as well as other arterial aneurysms (Dugan et al., 2015; Guo et al., 2018). Inter- and intrafamilial variability has been reported.

Spondyloepiphyseal dysplasia, Reardon type is an extremely rare type of spondyloepiphyseal dysplasia (see this term) described in several members of a single family to date and characterized by short stature, vertebral and femoral abnormalities, cervical instability and neurologic manifestations secondary to anomalies of the odontoid process.

A very rare genetic overgrowth/obesity syndrome with characteristics of macrocephaly, obesity, mental (intellectual) disability and ocular abnormalities. Other frequent clinical signs include macrosomia, downslanting palpebral fissures, hypertelorism, broad nasal root, high and broad forehead and delay in bone maturation, in association with normal thyroid function and karyotype.

Insulin-like growth factor I deficiency (IGF1D) is characterized by severe pre- and postnatal growth failure, sensorineural deafness, and impaired motor and intellectual development (summary by Bonapace et al., 2003).

CHST3-related skeletal dysplasia is characterized by short stature of prenatal onset, joint dislocations (knees, hips, radial heads), clubfeet, and limitation of range of motion that can involve all large joints. Kyphosis and occasionally scoliosis with slight shortening of the trunk develop in childhood. Minor heart valve dysplasia has been described in several persons. Intellect and vision are normal.

Larsen-like osseous dysplasia-short stature syndrome is a rare primary bone dysplasia characterized by a Larsen-like phenotype including multiple, congenital, large joint dislocations, craniofacial abnormalities (i.e. macrocephaly, flat occiput, prominent forehead, hypertelorism, low-set, malformed ears, flat nose, cleft palate), spinal abnormalities, cylindrical fingers, and talipes equinovarus, as well as growth retardation (resulting in short stature) and delayed bone age. Other reported clinical manifestations include severe developmental delay, hypotonia, clinodactyly, congenital heart defect and renal dysplasia.

CODAS is an acronym for cerebral, ocular, dental, auricular, and skeletal anomalies. CODAS syndrome is a rare disorder characterized by a distinctive constellation of features that includes developmental delay, craniofacial anomalies, cataracts, ptosis, median nasal groove, delayed tooth eruption, hearing loss, short stature, delayed epiphyseal ossification, metaphyseal hip dysplasia, and vertebral coronal clefts (summary by Strauss et al., 2015).

Kimberley-type spondyloepiphyseal dysplasia (SEDK) is a mild autosomal dominant SED with a phenotype of short stature, stocky build, and early-onset osteoarthritis of the weight-bearing joints (summary by Gleghorn et al., 2005).

Cataract-congenital heart disease-neural tube defect syndrome is a multiple congenital anomaly syndrome characterized by sacral neural tube defects resulting in tethered cord, atrial and/or ventricular septal heart defects (that are detected in infancy), bilateral, symmetrical hyperopia, rapidly progressive early childhood cataracts, bilateral aphakic glaucoma, and abnormal facial features (low frontal hairline, small ears, short philtrum, prominent, widely spaced central incisors, and micrognathia). Hypotonia, growth and developmental delay, seizures, and joint limitation are also reported.

Lipodystrophy-intellectual disability-deafness syndrome is an extremely rare form of genetic lipodystrophy (see this term), reported in 3 patients from one family to date, characterized by generalized congenital lipodystrophy, low birth weight, progressive sensorineural deafness occurring in childhood, intellectual deficit, progressive osteopenia, delayed skeletal maturation, skeletal abnormalities described as slender, undermineralized tubular bones, and dense metaphyseal striations in the distal femur, ulna and radius of older patients. Autosomal recessive inheritance has been suggested.

The constitutional deletion of chromosome 1p36 results in a syndrome with multiple congenital anomalies and mental retardation (Shapira et al., 1997). Monosomy 1p36 is the most common terminal deletion syndrome in humans, occurring in 1 in 5,000 births (Shaffer and Lupski, 2000; Heilstedt et al., 2003). See also neurodevelopmental disorder with or without anomalies of the brain, eye, or heart (NEDBEH; 616975), which shows overlapping features and is caused by heterozygous mutation in the RERE gene (605226) on proximal chromosome 1p36. See also Radio-Tartaglia syndrome (RATARS; 619312), caused by mutation in the SPEN gene (613484) on chromosome 1p36, which shows overlapping features.

IMAGe syndrome is an acronym for the major findings of intrauterine growth restriction (IUGR), metaphyseal dysplasia, adrenal hypoplasia congenita, and genitourinary abnormalities (in males). Findings reported in individuals with a clinical and/or molecular diagnosis include: IUGR; Some type of skeletal abnormality (most commonly delayed bone age and short stature, and occasionally, metaphyseal and epiphyseal dysplasia of varying severity); Adrenal insufficiency often presenting in the first month of life as an adrenal crisis or (rarely) later in childhood with failure to thrive and recurrent vomiting; Genital abnormalities in males (cryptorchidism, micropenis, and hypospadias) but not in females. Hypotonia and developmental delay are reported in some individuals; cognitive outcome appears to be normal in the majority of individuals.

X-linked spondyloepimetaphyseal dysplasia with hypomyelinating leukodystrophy (SEMDHL) is an X-linked recessive developmental disorder characterized by slowly progressive skeletal and neurologic abnormalities, including short stature, large and deformed joints, significant motor impairment, visual defects, and sometimes cognitive deficits. Affected individuals typically have normal early development in the first year or so of life, followed by development regression and the development of symptoms. Brain imaging shows white matter abnormalities consistent with hypomyelinating leukodystrophy (summary by Miyake et al., 2017).

The autosomal dominant TRPV4 disorders (previously considered to be clinically distinct phenotypes before their molecular basis was discovered) are now grouped into neuromuscular disorders and skeletal dysplasias; however, the overlap within each group is considerable. Affected individuals typically have either neuromuscular or skeletal manifestations alone, and in only rare instances an overlap syndrome has been reported. The three autosomal dominant neuromuscular disorders (mildest to most severe) are: Charcot-Marie-Tooth disease type 2C. Scapuloperoneal spinal muscular atrophy. Congenital distal spinal muscular atrophy. The autosomal dominant neuromuscular disorders are characterized by a congenital-onset, static, or later-onset progressive peripheral neuropathy with variable combinations of laryngeal dysfunction (i.e., vocal fold paresis), respiratory dysfunction, and joint contractures. The six autosomal dominant skeletal dysplasias (mildest to most severe) are: Familial digital arthropathy-brachydactyly. Autosomal dominant brachyolmia. Spondylometaphyseal dysplasia, Kozlowski type. Spondyloepiphyseal dysplasia, Maroteaux type. Parastremmatic dysplasia. Metatropic dysplasia. The skeletal dysplasia is characterized by brachydactyly (in all 6); the five that are more severe have short stature that varies from mild to severe with progressive spinal deformity and involvement of the long bones and pelvis. In the mildest of the autosomal dominant TRPV4 disorders life span is normal; in the most severe it is shortened. Bilateral progressive sensorineural hearing loss (SNHL) can occur with both autosomal dominant neuromuscular disorders and skeletal dysplasias.

PNPLA6 disorders span a phenotypic continuum characterized by variable combinations of cerebellar ataxia; upper motor neuron involvement manifesting as spasticity and/or brisk reflexes; chorioretinal dystrophy associated with variable degrees of reduced visual function; and hypogonadotropic hypogonadism (delayed puberty and lack of secondary sex characteristics). The hypogonadotropic hypogonadism occurs either in isolation or as part of anterior hypopituitarism (growth hormone, thyroid hormone, or gonadotropin deficiencies). Common but less frequent features are peripheral neuropathy (usually of axonal type manifesting as reduced distal reflexes, diminished vibratory sensation, and/or distal muscle wasting); hair anomalies (long eyelashes, bushy eyebrows, or scalp alopecia); short stature; and impaired cognitive functioning (learning disabilities in children; deficits in attention, visuospatial abilities, and recall in adults). Some of these features can occur in distinct clusters on the phenotypic continuum: Boucher-Neuhäuser syndrome (cerebellar ataxia, chorioretinal dystrophy, and hypogonadotropic hypogonadism); Gordon Holmes syndrome (cerebellar ataxia, hypogonadotropic hypogonadism, and – to a variable degree – brisk reflexes); Oliver-McFarlane syndrome (trichomegaly, chorioretinal dystrophy, short stature, intellectual disability, and hypopituitarism); Laurence-Moon syndrome; and spastic paraplegia type 39 (SPG39) (upper motor neuron involvement, peripheral neuropathy, and sometimes reduced cognitive functioning and/or cerebellar ataxia).

The FLNB disorders include a spectrum of phenotypes ranging from mild to severe. At the mild end are spondylocarpotarsal synostosis (SCT) syndrome and Larsen syndrome; at the severe end are the phenotypic continuum of atelosteogenesis types I (AOI) and III (AOIII) and Piepkorn osteochondrodysplasia (POCD). SCT syndrome is characterized by postnatal disproportionate short stature, scoliosis and lordosis, clubfeet, hearing loss, dental enamel hypoplasia, carpal and tarsal synostosis, and vertebral fusions. Larsen syndrome is characterized by congenital dislocations of the hip, knee, and elbow; clubfeet (equinovarus or equinovalgus foot deformities); scoliosis and cervical kyphosis, which can be associated with a cervical myelopathy; short, broad, spatulate distal phalanges; distinctive craniofacies (prominent forehead, depressed nasal bridge, malar flattening, and widely spaced eyes); vertebral anomalies; and supernumerary carpal and tarsal bone ossification centers. Individuals with SCT syndrome and Larsen syndrome can have midline cleft palate and hearing loss. AOI and AOIII are characterized by severe short-limbed dwarfism; dislocated hips, knees, and elbows; and clubfeet. AOI is lethal in the perinatal period. In individuals with AOIII, survival beyond the neonatal period is possible with intensive and invasive respiratory support. Piepkorn osteochondrodysplasia (POCD) is a perinatal-lethal micromelic dwarfism characterized by flipper-like limbs (polysyndactyly with complete syndactyly of all fingers and toes, hypoplastic or absent first digits, and duplicated intermediate and distal phalanges), macrobrachycephaly, prominant forehead, hypertelorism, and exophthalmos. Occasional features include cleft palate, omphalocele, and cardiac and genitourinary anomalies. The radiographic features at mid-gestation are characteristic.

Patients with mutations in the receptor for insulin-like growth factor I show intrauterine growth retardation and postnatal growth failure, resulting in short stature and microcephaly. Other features may include delayed bone age, developmental delay, and dysmorphic features.

Kowarski syndrome, or short stature associated with bioinactive growth hormone, is characterized clinically by normal or slightly increased GH secretion, pathologically low IGF1 (147440) levels, and normal catch-up growth on GH replacement therapy (Besson et al., 2005).

Noonan syndrome (NS) is characterized by characteristic facies, short stature, congenital heart defect, and developmental delay of variable degree. Other findings can include broad or webbed neck, unusual chest shape with superior pectus carinatum and inferior pectus excavatum, cryptorchidism, varied coagulation defects, lymphatic dysplasias, and ocular abnormalities. Although birth length is usually normal, final adult height approaches the lower limit of normal. Congenital heart disease occurs in 50%-80% of individuals. Pulmonary valve stenosis, often with dysplasia, is the most common heart defect and is found in 20%-50% of individuals. Hypertrophic cardiomyopathy, found in 20%-30% of individuals, may be present at birth or develop in infancy or childhood. Other structural defects include atrial and ventricular septal defects, branch pulmonary artery stenosis, and tetralogy of Fallot. Up to one fourth of affected individuals have mild intellectual disability, and language impairments in general are more common in NS than in the general population.

Wiedemann-Steiner syndrome (WSS) is characterized by developmental delay, intellectual disability, and characteristic facial features, with or without additional congenital anomalies. The facial features include thick eyebrows with lateral flare, vertically narrow and downslanted palpebral fissures, widely spaced eyes, long eyelashes, wide nasal bridge, broad nasal tip, thin vermilion of the upper lip, and thick scalp hair. About 60% of affected individuals have hypertrichosis cubiti ("hairy elbows"), which was once thought to be pathognomic for the syndrome, with a majority having hypertrichosis of other body parts. Other clinical features include feeding difficulties, prenatal and postnatal growth restriction, epilepsy, ophthalmologic anomalies, congenital heart defects, hand anomalies (such as brachydactyly and clinodactyly), hypotonia, vertebral anomalies (especially fusion anomalies of the cervical spine), renal and uterine anomalies, immune dysfunction, brain malformations, and dental anomalies.

A rare, primary bone dysplasia characterized by prenatal and postnatal growth retardation, short stature, cortical thickening and medullary stenosis of the long bones, absent diploic space in the skull bones, hypocalcemia due to the hypoparathyroidism, small hands and feet, delayed mental and motor development, intellectual disability, dental anomalies, and dysmorphic features, including prominent forehead, small deep-set eyes, beaked nose, and micrognathia.

Bamforth-Lazarus syndrome (BAMLAZ) is a rare autosomal recessive disorder characterized by congenital hypothyroidism due to thyroid agenesis or thyroid hypoplasia, cleft palate, and spiky hair, with or without choanal atresia or bifid epiglottis (summary by Sarma et al., 2022).

Hypoparathyroidism-retardation-dysmorphism syndrome (HRDS) is an autosomal recessive multisystem disorder characterized by intrauterine and postnatal growth retardation, infantile-onset hypoparathyroidism that can result in severe hypocalcemic seizures, dysmorphic facial features, and developmental delay (summary by Padidela et al., 2009 and Ratbi et al., 2015).

A very rare syndrome consisting of microcephaly with facial dysmorphism, spondylometaphyseal dysplasia and severe intellectual deficit. Eight cases have been reported in the literature in two unrelated families. Dysmorphic features include hypertelorism, depressed nasal bridge, and large nose with a large nasal tip, anteverted nostrils and wide mouth with thick lips. Affected patients do not achieve language ability. The condition is probably hereditary, and transmitted as an autosomal recessive trait.

Microcephalic osteodysplastic primordial dwarfism type I (MOPD1) is a severe autosomal recessive skeletal dysplasia characterized by dwarfism, microcephaly, and neurologic abnormalities, including mental retardation, brain malformations, and ocular/auditory sensory deficits. Patients often die in early childhood (summary by Pierce and Morse, 2012).

Ulna metaphyseal dysplasia syndrome is a rare primary bone dysplasia characterized by dysplasia of the distal ulnar metaphyses, as well as metacarpal/metatarsal dysplasia and metaphyseal changes resembling enchondromata. Patients usually present bony swelling of the wrists with or without pain (knees and ankles may also be affected). Other variably associated features include platyspondyly, skeletal development delay, short stature and coxa valga.

Trichorhinophalangeal syndrome (TRPS) is characterized by craniofacial and skeletal abnormalities. Craniofacial features include sparse, slowly growing scalp hair, laterally sparse eyebrows, a bulbous tip of the nose, protruding ears, long flat philtrum, and thin upper vermillion border. The most typical radiographic findings in TRPS are cone-shaped epiphyses, predominantly at the middle phalanges. Hip malformations such as coxa plana, coxa magna, or coxa vara are present in over 70% of patients. In older patients, the hip abnormalities resemble degenerative arthrosis. TRPS3 differs from TRPS1 by the presence of severe brachydactyly, due to short metacarpals, and severe short stature (summary by Ludecke et al., 2001).

Noonan syndrome (NS) is characterized by characteristic facies, short stature, congenital heart defect, and developmental delay of variable degree. Other findings can include broad or webbed neck, unusual chest shape with superior pectus carinatum and inferior pectus excavatum, cryptorchidism, varied coagulation defects, lymphatic dysplasias, and ocular abnormalities. Although birth length is usually normal, final adult height approaches the lower limit of normal. Congenital heart disease occurs in 50%-80% of individuals. Pulmonary valve stenosis, often with dysplasia, is the most common heart defect and is found in 20%-50% of individuals. Hypertrophic cardiomyopathy, found in 20%-30% of individuals, may be present at birth or develop in infancy or childhood. Other structural defects include atrial and ventricular septal defects, branch pulmonary artery stenosis, and tetralogy of Fallot. Up to one fourth of affected individuals have mild intellectual disability, and language impairments in general are more common in NS than in the general population.

A type of central congenital hypothyroidism with characteristics of low levels of thyroid hormones due to insufficient release of thyroid-stimulating hormone (TSH) caused by pituitary resistance to thyrotropin-releasing hormone (TRH). It may or may not be observed from birth. The clinical manifestations are often subtle, probably as a result of trans-placental passage of some maternal thyroid hormone or due to the fact that many infants have some thyroid production of their own. More specific symptoms and signs often do not develop until several months of age. Common clinical features and signs include decreased activity and increased sleep, feeding difficulty and constipation, prolonged jaundice. Slow linear growth and developmental delay are usually apparent by 4-6 months of age. Caused by mutations in the TRH receptor gene (TRHR; 8q23).

The brachydactyly type C (BDC) phenotype includes brachymesophalangy of fingers 2, 3, and 5. The fourth finger is usually unaffected and thus appears as the longest finger of the hand. Shortening of metacarpal 1 and hyperphalangy in fingers 2 and 3 may occur and can be considered relatively characteristic signs. BDC can be highly variable, ranging from severely affected hands with very short fingers to mildly affected cases with only moderate brachydactyly, most often affecting the middle and proximal phalanges of fingers 2 and 3 (summary by Lehmann et al., 2006).

Majeed syndrome (MJDS) is an autosomal recessive pediatric multisystem autoinflammatory disorder characterized by chronic recurrent multifocal osteomyelitis (CRMO) and congenital dyserythropoietic anemia; some patients may also develop neutrophilic dermatosis. Additional features may include fever, failure to thrive, and neutropenia. Laboratory studies show elevated inflammatory markers consistent with activation of the proinflammatory IL1 (147760) pathway (summary by Ferguson and El-Shanti, 2021). Genetic Heterogeneity of Chronic Recurrent Multifocal Osteomyelitis See also CRMO2 (612852), caused by mutation in the IL1RN gene (147679) on chromosome 2q14; and CRMO3 (259680), caused by mutation in the IL1R1 gene (147810) on chromosome 2q12.

RHYNS syndrome is characterized by gaze palsy, retinitis pigmentosa, sensorineural hearing loss, hypopituitarism, nephronophthisis, and mild skeletal dysplasia (Di Rocco et al., 1997).

Disorder with manifestations of moderate-to-severe metaphyseal changes, mild epiphyseal involvement, rhizomelic shortening of the lower limbs with bowing of the femora and/or tibiae, coxa vara, genu varum and pear-shaped vertebrae in childhood. The syndrome has been described in a large Missouri (US) kindred with 14 affected members in 4 generations. Though some spontaneous improvement of the skeletal defects may occur in adolescence, the affected individuals remained shorter than their age-matched unaffected siblings. Predisposition deformities to osteoarthritis have been noted. This condition is caused by mutation in the MMP13 gene (locus 11q22.3) and transmitted in an autosomal dominant manner.

Penttinen syndrome (PENTT) is characterized by a prematurely aged appearance involving lipoatrophy and epidermal and dermal atrophy, as well as hypertrophic lesions that resemble scars, thin hair, proptosis, underdeveloped cheekbones, and marked acroosteolysis (Johnston et al., 2015).

Weill-Marchesani syndrome (WMS) is a connective tissue disorder characterized by abnormalities of the lens of the eye, short stature, brachydactyly, joint stiffness, and cardiovascular defects. The ocular problems, typically recognized in childhood, include microspherophakia (small spherical lens), myopia secondary to the abnormal shape of the lens, ectopia lentis (abnormal position of the lens), and glaucoma, which can lead to blindness. Height of adult males is 142-169 cm; height of adult females is 130-157 cm. Autosomal recessive WMS cannot be distinguished from autosomal dominant WMS by clinical findings alone.

Congenital hypothyroidism can also occur as part of syndromes that affect other organs and tissues in the body. These forms of the condition are described as syndromic. Some common forms of syndromic hypothyroidism include Pendred syndrome, Bamforth-Lazarus syndrome, and brain-lung-thyroid syndrome.\n\nSigns and symptoms of congenital hypothyroidism result from the shortage of thyroid hormones. Affected babies may show no features of the condition, although some babies with congenital hypothyroidism are less active and sleep more than normal. They may have difficulty feeding and experience constipation. If untreated, congenital hypothyroidism can lead to intellectual disability and slow growth. In the United States and many other countries, all hospitals test newborns for congenital hypothyroidism. If treatment begins in the first two weeks after birth, infants usually develop normally.\n\nCongenital hypothyroidism occurs when the thyroid gland fails to develop or function properly. In 80 to 85 percent of cases, the thyroid gland is absent, severely reduced in size (hypoplastic), or abnormally located. These cases are classified as thyroid dysgenesis. In the remainder of cases, a normal-sized or enlarged thyroid gland (goiter) is present, but production of thyroid hormones is decreased or absent. Most of these cases occur when one of several steps in the hormone synthesis process is impaired; these cases are classified as thyroid dyshormonogenesis. Less commonly, reduction or absence of thyroid hormone production is caused by impaired stimulation of the production process (which is normally done by a structure at the base of the brain called the pituitary gland), even though the process itself is unimpaired. These cases are classified as central (or pituitary) hypothyroidism.\n\nCongenital hypothyroidism is a partial or complete loss of function of the thyroid gland (hypothyroidism) that affects infants from birth (congenital). The thyroid gland is a butterfly-shaped tissue in the lower neck. It makes iodine-containing hormones that play an important role in regulating growth, brain development, and the rate of chemical reactions in the body (metabolism). People with congenital hypothyroidism have lower-than-normal levels of these important hormones.

Wolf-Hirschhorn syndrome is a congenital malformation syndrome characterized by pre- and postnatal growth deficiency, developmental disability of variable degree, characteristic craniofacial features ('Greek warrior helmet' appearance of the nose, high forehead, prominent glabella, hypertelorism, high-arched eyebrows, protruding eyes, epicanthal folds, short philtrum, distinct mouth with downturned corners, and micrognathia), and a seizure disorder (Battaglia et al., 2008).

Aromatase deficiency is a rare autosomal recessive disorder in which individuals cannot synthesize endogenous estrogens. If a fetus lacks aromatase activity, dehydroepiandrosterone sulfate produced by the fetal adrenal glands cannot be converted to estrogen by the placenta, and is converted to testosterone peripherally and results in virilization of both fetus and mother. Virilization manifests as pseudohermaphroditism in female infants, with hirsutism and acne in the mother; the maternal indicators resolve following delivery. Affected females are usually diagnosed at birth because of the pseudohermaphroditism. Cystic ovaries and delayed bone maturation can occur during childhood and adolescence in these girls, who present at puberty with primary amenorrhea, failure of breast development, virilization, and hypergonadotropic hypogonadism. Affected males do not present with obvious defects at birth. Their clinical symptoms include tall stature, delayed skeletal maturation, delayed epiphyseal closure, bone pain, eunuchoid body proportions, and excess adiposity. Estrogen replacement therapy reverses the symptoms in males and females (summary by Jones et al., 2007).

This syndrome is characterized by exocrine pancreatic insufficiency, dyserythropoietic anemia, and calvarial hyperostosis. It has been described in four children, three boys and one girl, from two consanguineous families. The disease is due to a mutation in the COX4I2 gene, encoding a mitochondrial cytochrome C oxidase sub-unit. Transmission is autosomal recessive.

SLC25A24 Fontaine progeroid syndrome is a multisystem connective tissue disorder characterized by poor growth, abnormal skeletal features, and distinctive craniofacial features with sagging, thin skin, and decreased subcutaneous fat suggesting an aged appearance that is most pronounced in infancy and improves with time. Characteristic radiographic features include turribrachycephaly with widely open anterior fontanelle, craniosynostosis, and anomalies of the terminal phalanges. Cardiovascular, genitourinary, ocular, and gastrointestinal abnormalities may also occur. To date, 13 individuals with a molecularly confirmed diagnosis of SLC25A24 Fontaine progeroid syndrome have been described.

A rare genetic bone development disorder with characteristics of hand camptodactyly associated with facial dysmorphism (flat face, hypertelorism, telecanthus, symblepharon, simplified ears, retrognathia) and neck anomalies (short neck with pterygia, muscle sclerosis). Additional features include spinal defects (e.g. cervical and dorso-lumbar spina bifida occulta), congenital shortness of the sternocleidomastoid muscle, flexed wrists and thin hands and feet. Brain structural anomalies, multiple nevi, micropenis and mild intellectual disability are also observed. Imaging reveals widened femoral necks, cortical thickening of long bones and delayed bone age.

Turner-type X-linked syndromic intellectual developmental disorder (MRXST) is a neurodevelopmental disorder with a highly variable phenotype. Some affected families show X-linked recessive inheritance, with only males being affected and carrier females having no abnormal findings. In other affected families, males are severely affected, and female mutation carriers show milder cognitive abnormalities or dysmorphic features. In addition, there are female patients with de novo mutations who show the full phenotype, despite skewed X-chromosome inactivation. Affected individuals show global developmental delay from infancy, with variably impaired intellectual development and poor or absent speech, often with delayed walking. Dysmorphic features are common and can include macrocephaly, microcephaly, deep-set eyes, hypotelorism, small palpebral fissures, dysplastic, large, or low-set ears, long face, bitemporal narrowing, high-arched palate, thin upper lip, and scoliosis or mild distal skeletal anomalies, such as brachydactyly or tapered fingers. Males tend to have cryptorchidism. Other features, such as hypotonia, seizures, and delayed bone age, are more variable (summary by Moortgat et al., 2018).

Three M syndrome is characterized by severe pre- and postnatal growth deficiency (final height 5-6 SD below the mean; i.e., 120-130 cm), characteristic facies, and normal intelligence. Additional features of three M syndrome include short broad neck, prominent trapezii, deformed sternum, short thorax, square shoulders, winged scapulae, hyperlordosis, short fifth fingers, prominent heels, and loose joints. Males with three M syndrome have hypogonadism and occasionally hypospadias.

Isolated growth hormone deficiency type IB (IGH1B) is an autosomal recessive disorder characterized by low but detectable levels of GH, short stature (more than 2 SD below the mean for age and sex), delayed bone age, and a good response to rhGH treatment without antibody formation (summary by Alatzoglou et al., 2014). For general phenotypic information and a discussion of genetic heterogeneity of IGHD, see 262400.

Autosomal recessive form of oculodentodigital dysplasia.

Autosomal recessive spondylometaphyseal dysplasia, Mégarbané type is a rare, primary bone dysplasia characterized by intrauterine growth retardation, pre- and postnatal disproportionate short stature with short, rhizomelic limbs, facial dysmorphism, a short neck and small thorax. Hypotonia, cardiomegaly and global developmental delay have also been associated. Several radiographic findings have been reported, including ribs with cupped ends, platyspondyly, square iliac bones, horizontal and trident acetabula, hypoplastic ischia, and delayed epiphyseal ossification.

Researchers have described several forms of hereditary hypophosphatemic rickets, which are distinguished by their pattern of inheritance and genetic cause. The most common form of the disorder is known as X-linked hypophosphatemic rickets (XLH). It has an X-linked dominant pattern of inheritance. X-linked recessive, autosomal dominant, and autosomal recessive forms of the disorder are much rarer.\n\nAnother rare type of the disorder is known as hereditary hypophosphatemic rickets with hypercalciuria (HHRH). In addition to hypophosphatemia, this condition is characterized by the excretion of high levels of calcium in the urine (hypercalciuria).\n\nOther signs and symptoms of hereditary hypophosphatemic rickets can include premature fusion of the skull bones (craniosynostosis) and dental abnormalities. The disorder may also cause abnormal bone growth where ligaments and tendons attach to joints (enthesopathy). In adults, hypophosphatemia is characterized by a softening of the bones known as osteomalacia.\n\nIn most cases, the signs and symptoms of hereditary hypophosphatemic rickets begin in early childhood. The features of the disorder vary widely, even among affected members of the same family. Mildly affected individuals may have hypophosphatemia without other signs and symptoms. More severely affected children experience slow growth and are shorter than their peers. They develop bone abnormalities that can interfere with movement and cause bone pain. The most noticeable of these abnormalities are bowed legs or knock knees. These abnormalities become apparent with weight-bearing activities such as walking. If untreated, they tend to worsen with time.\n\nHereditary hypophosphatemic rickets is a disorder related to low levels of phosphate in the blood (hypophosphatemia). Phosphate is a mineral that is essential for the normal formation of bones and teeth.

A rare syndrome with characteristics of pre-natal onset growth retardation (low birth weight and short stature), hypotonia, developmental delay and intellectual disability associated with microcephaly and craniofacial (low anterior hairline, hypotelorism, thick lips with carp-shaped mouth, high-arched palate, low-set ears), cardiac (conotruncal heart malformations such as tetralogy of Fallot) and skeletal (hypoplastic thumbs and first metacarpals) abnormalities.

Three M syndrome is characterized by severe pre- and postnatal growth deficiency (final height 5-6 SD below the mean; i.e., 120-130 cm), characteristic facies, and normal intelligence. Additional features of three M syndrome include short broad neck, prominent trapezii, deformed sternum, short thorax, square shoulders, winged scapulae, hyperlordosis, short fifth fingers, prominent heels, and loose joints. Males with three M syndrome have hypogonadism and occasionally hypospadias.

Self-limited delayed puberty (DPSL) is characterized by delayed development of Tanner stage G2 accompanied by low serum gonadotropins. Affected individuals experience spontaneous attainment of Tanner stage G4 by 18 years of age, with normalization of gonadotropins, which excludes a diagnosis of hypogonadotropic hypogonadism (see 147950) (Mancini et al., 2020).

Congenital disorders of glycosylation (CDGs) that represent defects of dolichol-linked oligosaccharide assembly are classified as CDG type I. For a general description and a discussion of the classification of CDGs, see CDG1A (212065).

Cystinosis comprises three allelic phenotypes: Nephropathic cystinosis in untreated children is characterized by renal Fanconi syndrome, poor growth, hypophosphatemic/calcipenic rickets, impaired glomerular function resulting in complete glomerular failure, and accumulation of cystine in almost all cells, leading to cellular dysfunction with tissue and organ impairment. The typical untreated child has short stature, rickets, and photophobia. Failure to thrive is generally noticed after approximately age six months; signs of renal tubular Fanconi syndrome (polyuria, polydipsia, dehydration, and acidosis) appear as early as age six months; corneal crystals can be present before age one year and are always present after age 16 months. Prior to the use of renal transplantation and cystine-depleting therapy, the life span in nephropathic cystinosis was no longer than ten years. With these interventions, affected individuals can survive at least into the mid-forties or fifties with satisfactory quality of life. Intermediate cystinosis is characterized by all the typical manifestations of nephropathic cystinosis, but onset is at a later age. Renal glomerular failure occurs in all untreated affected individuals, usually between ages 15 and 25 years. The non-nephropathic (ocular) form of cystinosis is characterized clinically only by photophobia resulting from corneal cystine crystal accumulation.

Cardiospondylocarpofacial syndrome (CSCF) is characterized by growth retardation, dysmorphic facial features, brachydactyly with carpal-tarsal fusion, extensive posterior cervical vertebral synostosis, cardiac septal defects with valve dysplasia, and deafness with inner ear malformations (summary by Le Goff et al., 2016).

Syndromic multisystem autoimmune disease due to Itch deficiency is a rare, genetic, systemic autoimmune disease characterized by failure to thrive, global developmental delay, distinctive craniofacial dysmorphism (relative macrocephaly, dolichocephaly, frontal bossing, orbital proptosis, flattened midface with a prominent occiput, low, posteriorly rotated ears, micrognatia), hepato- and/or splenomegaly, and multisystemic autoimmune disease involving the lungs, liver, gut and/or thyroid gland.

14q11.2 microdeletion syndrome is a recently described syndrome characterized by developmental delay, hypotonia and facial dysmorphism.

The 4q21 microdeletion syndrome is a newly described syndrome associated with facial dysmorphism, progressive growth restriction, severe intellectual deficit and absent or severely delayed speech.

Noonan syndrome with multiple lentigines (NSML) is a condition in which the cardinal features consist of lentigines, hypertrophic cardiomyopathy, short stature, pectus deformity, and dysmorphic facial features including widely spaced eyes and ptosis. Multiple lentigines present as dispersed flat, black-brown macules, mostly on the face, neck, and upper part of the trunk with sparing of the mucosa. In general, lentigines do not appear until age four to five years but then increase to the thousands by puberty. Some individuals with NSML do not exhibit lentigines. Approximately 85% of affected individuals have heart defects, including hypertrophic cardiomyopathy (typically appearing during infancy and sometimes progressive) and pulmonary valve stenosis. Postnatal growth restriction resulting in short stature occurs in fewer than 50% of affected persons, although most affected individuals have a height that is less than the 25th centile for age. Sensorineural hearing deficits, present in approximately 20% of affected individuals, are poorly characterized. Intellectual disability, typically mild, is observed in approximately 30% of persons with NSML.

Meier-Gorlin syndrome is a condition primarily characterized by short stature. It is considered a form of primordial dwarfism because the growth problems begin before birth (intrauterine growth retardation). After birth, affected individuals continue to grow at a slow rate. Other characteristic features of this condition are underdeveloped or missing kneecaps (patellae), small ears, and, often, an abnormally small head (microcephaly). Despite a small head size, most people with Meier-Gorlin syndrome have normal intellect.\n\nAbnormalities in sexual development may also occur in Meier-Gorlin syndrome. In some males with this condition, the testes are small or undescended (cryptorchidism). Affected females may have unusually small external genital folds (hypoplasia of the labia majora) and small breasts. Both males and females with this condition can have sparse or absent underarm (axillary) hair.\n\nMost people with Meier-Gorlin syndrome have distinctive facial features. In addition to being abnormally small, the ears may be low-set or rotated backward. Additional features can include a small mouth (microstomia), an underdeveloped lower jaw (micrognathia), full lips, and a narrow nose with a high nasal bridge.\n\nSome people with Meier-Gorlin syndrome have other skeletal abnormalities, such as unusually narrow long bones in the arms and legs, a deformity of the knee joint that allows the knee to bend backwards (genu recurvatum), and slowed mineralization of bones (delayed bone age).\n\nAdditional features of Meier-Gorlin syndrome can include difficulty feeding and a lung condition known as pulmonary emphysema or other breathing problems.

Additional features of Meier-Gorlin syndrome can include difficulty feeding and a lung condition known as pulmonary emphysema or other breathing problems.\n\nSome people with Meier-Gorlin syndrome have other skeletal abnormalities, such as unusually narrow long bones in the arms and legs, a deformity of the knee joint that allows the knee to bend backwards (genu recurvatum), and slowed mineralization of bones (delayed bone age).\n\nMost people with Meier-Gorlin syndrome have distinctive facial features. In addition to being abnormally small, the ears may be low-set or rotated backward. Additional features can include a small mouth (microstomia), an underdeveloped lower jaw (micrognathia), full lips, and a narrow nose with a high nasal bridge.\n\nAbnormalities in sexual development may also occur in Meier-Gorlin syndrome. In some males with this condition, the testes are small or undescended (cryptorchidism). Affected females may have unusually small external genital folds (hypoplasia of the labia majora) and small breasts. Both males and females with this condition can have sparse or absent underarm (axillary) hair.\n\nMeier-Gorlin syndrome is a condition primarily characterized by short stature. It is considered a form of primordial dwarfism because the growth problems begin before birth (intrauterine growth retardation). After birth, affected individuals continue to grow at a slow rate. Other characteristic features of this condition are underdeveloped or missing kneecaps (patellae), small ears, and, often, an abnormally small head (microcephaly). Despite a small head size, most people with Meier-Gorlin syndrome have normal intellect.

Meier-Gorlin syndrome-4 (MGORS4) is a rare autosomal recessive disorder with the hallmarks of short stature, small external ears, and reduced or absent patellae. Breast hypoplasia is present in females (Guernsey et al., 2011). For a general phenotypic description and a discussion of genetic heterogeneity of Meier-Gorlin syndrome, see 224690.

Additional features of Meier-Gorlin syndrome can include difficulty feeding and a lung condition known as pulmonary emphysema or other breathing problems.\n\nSome people with Meier-Gorlin syndrome have other skeletal abnormalities, such as unusually narrow long bones in the arms and legs, a deformity of the knee joint that allows the knee to bend backwards (genu recurvatum), and slowed mineralization of bones (delayed bone age).\n\nMost people with Meier-Gorlin syndrome have distinctive facial features. In addition to being abnormally small, the ears may be low-set or rotated backward. Additional features can include a small mouth (microstomia), an underdeveloped lower jaw (micrognathia), full lips, and a narrow nose with a high nasal bridge.\n\nAbnormalities in sexual development may also occur in Meier-Gorlin syndrome. In some males with this condition, the testes are small or undescended (cryptorchidism). Affected females may have unusually small external genital folds (hypoplasia of the labia majora) and small breasts. Both males and females with this condition can have sparse or absent underarm (axillary) hair.\n\nMeier-Gorlin syndrome is a condition primarily characterized by short stature. It is considered a form of primordial dwarfism because the growth problems begin before birth (intrauterine growth retardation). After birth, affected individuals continue to grow at a slow rate. Other characteristic features of this condition are underdeveloped or missing kneecaps (patellae), small ears, and, often, an abnormally small head (microcephaly). Despite a small head size, most people with Meier-Gorlin syndrome have normal intellect.

Seckel syndrome is an autosomal recessive disorder characterized by proportionate short stature, severe microcephaly, mental retardation, and a typical 'bird-head' facial appearance (summary by Kalay et al., 2011). For a general phenotypic description and a discussion of genetic heterogeneity of Seckel syndrome, see 210600.

Ogden syndrome (OGDNS) is an X-linked neurodevelopmental disorder characterized by postnatal growth failure, severely delayed psychomotor development, variable dysmorphic features, and hypotonia. Many patients also have cardiac malformations or arrhythmias (summary by Popp et al., 2015).

Geleophysic dysplasia, a progressive condition resembling a lysosomal storage disorder, is characterized by short stature, short hands and feet, progressive joint limitation and contractures, distinctive facial features, progressive cardiac valvular disease, and thickened skin. Intellect is normal. Major findings are likely to be present in the first year of life. Cardiac, respiratory, and lung involvement result in death before age five years in approximately 33% of individuals with ADAMTSL2-related geleophysic dysplasia.

CHST3-related skeletal dysplasia is characterized by short stature of prenatal onset, joint dislocations (knees, hips, radial heads), clubfeet, and limitation of range of motion that can involve all large joints. Kyphosis and occasionally scoliosis with slight shortening of the trunk develop in childhood. Minor heart valve dysplasia has been described in several persons. Intellect and vision are normal.

Mosaic variegated aneuploidy syndrome is an autosomal recessive disorder characterized by poor growth and variable phenotypic manifestations, such as facial dysmorphism and congenital heart defects, associated with mosaic aneuploidies resulting from defects in cell division (summary by Snape et al., 2011). See also MVA1 (257300), caused by mutation in the BUB1B gene (602860) on chromosome 15q15.

Geleophysic dysplasia, a progressive condition resembling a lysosomal storage disorder, is characterized by short stature, short hands and feet, progressive joint limitation and contractures, distinctive facial features, progressive cardiac valvular disease, and thickened skin. Intellect is normal. Major findings are likely to be present in the first year of life. Cardiac, respiratory, and lung involvement result in death before age five years in approximately 33% of individuals with ADAMTSL2-related geleophysic dysplasia.

Any hypothyroidism, congenital, nongoitrous in which the cause of the disease is a mutation in the THRA gene.

Coffin-Siris syndrome (CSS) is classically characterized by aplasia or hypoplasia of the distal phalanx or nail of the fifth and additional digits, developmental or cognitive delay of varying degree, distinctive facial features, hypotonia, hirsutism/hypertrichosis, and sparse scalp hair. Congenital anomalies can include malformations of the cardiac, gastrointestinal, genitourinary, and/or central nervous systems. Other findings commonly include feeding difficulties, slow growth, ophthalmologic abnormalities, and hearing impairment.

Among the Yakuts, an Asian population isolate that is located in the northeastern part of Siberia, Maksimova et al. (2010) ascertained an autosomal recessive short stature syndrome involving postnatal growth failure, small hands and feet, loss of visual acuity with abnormalities of color vision, abnormal nuclear shape in neutrophil granulocytes (Pelger-Huet anomaly; see 169400), and normal intelligence.

Isolated gonadotropin-releasing hormone (GnRH) deficiency (IGD) is characterized by inappropriately low serum concentrations of the gonadotropins LH (luteinizing hormone) and FSH (follicle-stimulating hormone) in the presence of low circulating concentrations of sex steroids. IGD is associated with a normal sense of smell (normosmic IGD) in approximately 40% of affected individuals and an impaired sense of smell (Kallmann syndrome) in approximately 60%. IGD can first become apparent in infancy, adolescence, or adulthood. Infant boys with congenital IGD often have micropenis and cryptorchidism. Adolescents and adults with IGD have clinical evidence of hypogonadism and incomplete sexual maturation on physical examination. Adult males with IGD tend to have prepubertal testicular volume (i.e., <4 mL), absence of secondary sexual features (e.g., facial and axillary hair growth, deepening of the voice), decreased muscle mass, diminished libido, erectile dysfunction, and infertility. Adult females have little or no breast development and primary amenorrhea. Although skeletal maturation is delayed, the rate of linear growth is usually normal except for the absence of a distinct pubertal growth spurt.

Isolated gonadotropin-releasing hormone (GnRH) deficiency (IGD) is characterized by inappropriately low serum concentrations of the gonadotropins LH (luteinizing hormone) and FSH (follicle-stimulating hormone) in the presence of low circulating concentrations of sex steroids. IGD is associated with a normal sense of smell (normosmic IGD) in approximately 40% of affected individuals and an impaired sense of smell (Kallmann syndrome) in approximately 60%. IGD can first become apparent in infancy, adolescence, or adulthood. Infant boys with congenital IGD often have micropenis and cryptorchidism. Adolescents and adults with IGD have clinical evidence of hypogonadism and incomplete sexual maturation on physical examination. Adult males with IGD tend to have prepubertal testicular volume (i.e., <4 mL), absence of secondary sexual features (e.g., facial and axillary hair growth, deepening of the voice), decreased muscle mass, diminished libido, erectile dysfunction, and infertility. Adult females have little or no breast development and primary amenorrhea. Although skeletal maturation is delayed, the rate of linear growth is usually normal except for the absence of a distinct pubertal growth spurt.

Coffin-Siris syndrome is a congenital malformation syndrome characterized by developmental delay, intellectual disability, coarse facial features, feeding difficulties, and hypoplastic or absent fifth fingernails and fifth distal phalanges. Other more variable features may also occur. Patients with ARID1A mutations have a wide spectrum of manifestations, from severe intellectual disability and serious internal complications that could result in early death to mild intellectual disability (summary by Kosho et al., 2014). For a general phenotypic description and a discussion of genetic heterogeneity of Coffin-Siris syndrome, see CSS1 (135900). The chromosome 1p36.11 duplication syndrome, in which the ARID1A gene is duplicated, is characterized by impaired intellectual development, microcephaly, dysmorphic facial features, and hand and foot anomalies.

Coffin-Siris syndrome is a congenital malformation syndrome characterized by developmental delay, intellectual disability, coarse facial features, feeding difficulties, and hypoplastic or absent fifth fingernails and fifth distal phalanges. Other more variable features may also occur. Patients with SMARCB1 mutations may have more severe neurodevelopmental deficits including severe intellectual disability, brain structural abnormalities, and no expressive words, as well as scoliosis (summary by Kosho et al., 2014). For a general phenotypic description and a discussion of genetic heterogeneity of Coffin-Siris syndrome, see CSS1 (135900).

Coffin-Siris syndrome is a congenital malformation syndrome characterized by developmental delay, intellectual disability, coarse facial features, feeding difficulties, and hypoplastic or absent fifth fingernails and fifth distal phalanges. Other more variable features may also occur. Patients with SMARCA4 mutations may have less coarse craniofacial appearances and fewer behavioral abnormalities than Coffin-Siris patients with mutations in other genes (summary by Kosho et al., 2014). For a general phenotypic description and a discussion of genetic heterogeneity of Coffin-Siris syndrome, see CSS1 (135900).

Isolated gonadotropin-releasing hormone (GnRH) deficiency (IGD) is characterized by inappropriately low serum concentrations of the gonadotropins LH (luteinizing hormone) and FSH (follicle-stimulating hormone) in the presence of low circulating concentrations of sex steroids. IGD is associated with a normal sense of smell (normosmic IGD) in approximately 40% of affected individuals and an impaired sense of smell (Kallmann syndrome) in approximately 60%. IGD can first become apparent in infancy, adolescence, or adulthood. Infant boys with congenital IGD often have micropenis and cryptorchidism. Adolescents and adults with IGD have clinical evidence of hypogonadism and incomplete sexual maturation on physical examination. Adult males with IGD tend to have prepubertal testicular volume (i.e., <4 mL), absence of secondary sexual features (e.g., facial and axillary hair growth, deepening of the voice), decreased muscle mass, diminished libido, erectile dysfunction, and infertility. Adult females have little or no breast development and primary amenorrhea. Although skeletal maturation is delayed, the rate of linear growth is usually normal except for the absence of a distinct pubertal growth spurt.

Microcephalic primordial dwarfism, Dauber type is a rare, genetic developmental defect during embryogenesis characterized by severe pre- and postnatal growth retardation, severe microcephaly, severe developmental delay and intelletual disability, severe adult short stature and facial dysmorphism (incl. hypotelorism, small ears, prominent nose). Other reported features include skeletal anomalies (Madelung deformity, clinodactyly, mild lumbar scoliosis, bilateral hip dysplasia) and seizures. Absence of thelarche and menarche is also associated.

Combined methylmalonic aciduria (MMA) and homocystinuria is a genetically heterogeneous metabolic disorder of cobalamin (cbl; vitamin B12) metabolism, which is essential for hematologic and neurologic function. Biochemically, the defect causes decreased levels of the coenzymes adenosylcobalamin (AdoCbl) and methylcobalamin (MeCbl), which results in decreased activity of the respective enzymes methylmalonyl-CoA mutase (MUT; 609058) and methyltetrahydrofolate:homocysteine methyltransferase, also known as methionine synthase (MTR; 156570). The cblJ type is phenotypically and biochemically similar to the cblF type (MAHCF; 277380) (summary by Coelho et al., 2012).

Estrogen resistance (ESTRR) is characterized by absence of puberty with elevated estradiol and gonadotropic hormones, as well as markedly delayed bone maturation. Female patients show absent breast development, small uterus, and enlarged multicystic ovaries; male patients may show small testes (Bernard et al., 2017). Some patients exhibit continued growth into adulthood (Smith et al., 1994).

Multiple congenital anomalies-hypotonia-seizures syndrome is an autosomal recessive disorder characterized by neonatal hypotonia, lack of psychomotor development, seizures, dysmorphic features, and variable congenital anomalies involving the cardiac, urinary, and gastrointestinal systems. Most affected individuals die before 3 years of age (summary by Maydan et al., 2011). The disorder is caused by a defect in glycosylphosphatidylinositol (GPI) biosynthesis. For a discussion of genetic heterogeneity of MCAHS, see MCAHS1 (614080). For a discussion of genetic heterogeneity of GPI biosynthesis defects, see GPIBD1 (610293).

Combined immunodeficiency due to MALT1 deficiency is a rare, genetic form of primary immunodeficiency characterized by growth retardation, early recurrent pulmonary infections leading to bronchiectasis, inflammatory gastrointestinal disease, and other symptoms, such as rash, dermatitis, skin infections.

Hennekam lymphangiectasia-lymphedema syndrome (HKLLS1) is an autosomal recessive disorder characterized by generalized lymphatic dysplasia affecting various organs, including the intestinal tract, pericardium, and limbs. Additional features of the disorder include facial dysmorphism and cognitive impairment (summary by Alders et al., 2014). Genetic Heterogeneity of Hennekam Lymphangiectasia-Lymphedema Syndrome See also HKLLS2 (616006), caused by mutation in the FAT4 gene (612411) on chromosome 4q28, and HKLLS3 (618154), caused by mutation in the ADAMTS3 gene (605011) on chromosome 4q13.

A rare genetic disorder of sex development characterized by primary amenorrhea, short stature, delayed bone age, decreased levels of estradiol, elevated levels of follicle-stimulating hormone and luteinizing hormone, absent or underdeveloped uterus and ovaries, delayed development of pubic and axillary hair and normal 46,XX karyotype.

Ruijs et al. (2003) reported a Moroccan boy with a chromosomal breakage who died of hepatocellular carcinoma at age 17 years. The boy was noted to have growth retardation at age 3 years; at age 7 he was found to have thoracic kyphosis, frontal bossing, and a delayed bone age of approximately 3 years. He underwent surgery for severe bilateral posterior subcapsular cataracts at age 14. Examination at age 15 showed short stature and low weight, with premature graying of scalp hair, small frontotemporal diameter, small deep-set eyes, bulbous nose with high nasal bridge, small upper lip, and micrognathia. In addition, he had thoracic kyphoscoliosis, sloping shoulders, mild pectus excavatum, moderate bilateral contractures of both elbows, bilateral clinodactyly, and pes planus. At age 17, he developed abdominal pain, and ultrasonography revealed a liver mass; biopsy confirmed hepatocellular carcinoma. Because of the advanced stage, no treatment was possible, and he died 2 months later. Although his parents were not known to be consanguineous, they originated from the same small Moroccan village. Lessel et al. (2014) studied 2 brothers from a nonconsanguineous Australian family of European ancestry who exhibited low body weight, micrognathia, triangular face, muscular atrophy, lipodystrophy, bilateral simian creases, delayed bone age, and mild joint restrictions in the fingers and elbows. In addition, both brothers developed early-onset hepatocellular carcinoma, at ages 16 and 14 years, respectively. The older brother died at age 18 from complications of acute fulminant hepatic failure. Analysis of patient tumor biopsies showed strong focal accumulations of cancer biomarkers as well as a high proliferative index compared to healthy liver or to cells from idiopathic hepatocellular carcinoma.

Cerebellofaciodental syndrome is an autosomal recessive neurodevelopmental disorder characterized by delayed development, intellectual disability, abnormal facial and dental findings, and cerebellar hypoplasia (summary by Borck et al., 2015).

Any Meier-Gorlin syndrome in which the cause of the disease is a mutation in the GMNN gene.

Microcephaly, short stature, and impaired glucose metabolism-2 (MSSGM2) is an autosomal recessive syndrome characterized by microcephaly associated with impaired intellectual development, and short stature. Patients develop diabetes in the second or third decade of life, and hypothyroidism and delayed puberty have also been reported (Abdulkarim et al., 2015; Kernohan et al., 2015). For a discussion of genetic heterogeneity of microcephaly, short stature, and impaired glucose metabolism, see MSSGM1 (616033).

Silver-Russell syndrome-3 (SRS3) is characterized by intrauterine growth retardation with relative macrocephaly, followed by feeding difficulties and postnatal growth restriction. Dysmorphic facial features include triangular face, prominent forehead, and low-set ears. Other variable features include limb defects, genitourinary and cardiovascular anomalies, hearing impairment, and developmental delay (Begemann et al., 2015; Yamoto et al., 2017). For a discussion of genetic heterogeneity of Silver-Russell syndrome, see SRS1 (180860).

Any autosomal dominant non-syndromic intellectual disability in which the cause of the disease is a mutation in the DPP6 gene.

Short stature with nonspecific skeletal abnormalities-1 (SNSK1) is an autosomal dominant disorder characterized by height that is significantly shorter than that of noncarrier family members. Increased arm span to height, increased sitting height to total height, delayed bone age, and metacarpal shortening have been observed (Olney et al., 2006; Vasques et al., 2013). Biallelic mutation in the NPR2 gene causes acromesomelic dysplasia-1, Maroteaux type (AMD1; 602875). Genetic Heterogeneity of Short Stature with Nonspecific Skeletal Abnormalities SNSK2 (BDA1; 112500) is caused by heterozygous mutation in the IHH gene (600726) on chromosome 2q35.

About half of all people with trichothiodystrophy have a photosensitive form of the disorder, which causes them to be extremely sensitive to ultraviolet (UV) rays from sunlight. They develop a severe sunburn after spending just a few minutes in the sun. However, for reasons that are unclear, they do not develop other sun-related problems such as excessive freckling of the skin or an increased risk of skin cancer. Many people with trichothiodystrophy report that they do not sweat.\n\nTrichothiodystrophy is also associated with recurrent infections, particularly respiratory infections, which can be life-threatening. People with trichothiodystrophy may have abnormal red blood cells, including red blood cells that are smaller than normal. They may also have elevated levels of a type of hemoglobin called A2, which is a protein found in red blood cells. Other features of trichothiodystrophy can include dry, scaly skin (ichthyosis); abnormalities of the fingernails and toenails; clouding of the lens in both eyes from birth (congenital cataracts); poor coordination; and skeletal abnormalities including degeneration of both hips at an early age.\n\nIntellectual disability and delayed development are common in people with trichothiodystrophy, although most affected individuals are highly social with an outgoing and engaging personality. Some people with trichothiodystrophy have brain abnormalities that can be seen with imaging tests. A common neurological feature of this disorder is impaired myelin production (dysmyelination). Myelin is a fatty substance that insulates nerve cells and promotes the rapid transmission of nerve impulses.\n\nMothers of children with trichothiodystrophy may experience problems during pregnancy including pregnancy-induced high blood pressure (preeclampsia) and a related condition called HELLP syndrome that can damage the liver. Babies with trichothiodystrophy are at increased risk of premature birth, low birth weight, and slow growth. Most children with trichothiodystrophy have short stature compared to others their age. \n\nThe signs and symptoms of trichothiodystrophy vary widely. Mild cases may involve only the hair. More severe cases also cause delayed development, significant intellectual disability, and recurrent infections; severely affected individuals may survive only into infancy or early childhood.\n\nIn people with trichothiodystrophy, tests show that the hair is lacking sulfur-containing proteins that normally gives hair its strength. A cross section of a cut hair shows alternating light and dark banding that has been described as a "tiger tail."\n\nTrichothiodystrophy, commonly called TTD, is a rare inherited condition that affects many parts of the body. The hallmark of this condition is hair that is sparse and easily broken. 

Witteveen-Kolk syndrome (WITKOS) is an autosomal dominant disorder with characteristic distinctive facial features, microcephaly, short stature, and mildly impaired intellectual development with delayed cognitive and motor development and subtle anomalies on MRI-brain imaging (summary by Balasubramanian et al., 2021).

Anauxetic dysplasia is a spondyloepimetaphyseal dysplasia characterized by severe short stature of prenatal onset, very short adult height (less than 1 meter), hypodontia, midface hypoplasia, and mild intellectual disability. Vertebrae are ovoid with concave dorsal surfaces in the lumbar region and show delayed bone maturation. Femoral heads and necks are hypoplastic, as are the iliac bodies. Long bones show irregular mineralization of the metaphyses. The first and fifth metacarpals are short and wide with small, late-ossifying epiphyses and bullet-shaped middle phalanges (summary by Barraza-Garcia et al., 2017). For a discussion of genetic heterogeneity of anauxetic dysplasia, see ANXD1 (607095).

An inherited condition caused by autosomal dominant mutation(s) in the PPP1CB gene, encoding serine/threonine-protein phosphatase PP1-beta catalytic subunit. The condition is characterized by facial features similar to those seen in Noonan syndrome but may also include short stature, cognitive deficits, relative macrocephaly, small posterior fossa resulting in Chiari I malformation, hypernasal voice, cardiac defects, and ectodermal abnormalities, which typically presents as slow-growing, sparse, and/or unruly hair.

MISSLA is an autosomal recessive disorder characterized by intrauterine growth retardation, microcephaly, variable short stature, and limb abnormalities mainly affecting the upper limb and radial ray. Affected individuals typically have mild intellectual disability, but may have normal development (summary by Reynolds et al., 2017).

Mitochondrial myopathy and ataxia (MMYAT) is an autosomal recessive mtDNA depletion disorder characterized by cerebellar ataxia, congenital muscle involvement with histologic findings ranging from myopathic to dystrophic, and pigmentary retinopathy (summary by Donkervoort et al., 2019).

IMDDHH is a multisystem disorder characterized by immunodeficiency, mildly delayed psychomotor development, poor overall growth from infancy, and hypohomocysteinemia. Additional features, such as congenital heart defects and liver involvement, are more variable (summary by Huppke et al., 2017).

Geleophysic dysplasia, a progressive condition resembling a lysosomal storage disorder, is characterized by short stature, short hands and feet, progressive joint limitation and contractures, distinctive facial features, progressive cardiac valvular disease, and thickened skin. Intellect is normal. Major findings are likely to be present in the first year of life. Cardiac, respiratory, and lung involvement result in death before age five years in approximately 33% of individuals with ADAMTSL2-related geleophysic dysplasia.

Seckel syndrome is a rare autosomal recessive disorder characterized by intrauterine growth retardation, dwarfism, microcephaly with mental retardation, and a characteristic 'bird-headed' facial appearance (Shanske et al., 1997). Genetic Heterogeneity of Seckel Syndrome Other forms of Seckel syndrome include SCKL2 (606744), caused by mutation in the RBBP8 gene (604124) on chromosome 18q11; SCKL4 (613676), caused by mutation in the CENPJ gene (609279) on chromosome 13q12; SCKL5 (613823), caused by mutation in the CEP152 gene (613529) on chromosome 15q21; SCKL6 (614728), caused by mutation in the CEP63 gene (614724) on chromosome 3q22; SCKL7 (614851), caused by mutation in the NIN gene (608684) on chromosome 14q22; SCKL8 (615807), caused by mutation in the DNA2 gene (601810) on chromosome 10q21; SCKL9 (616777), caused by mutation in the TRAIP gene (605958) on chromosome 3p21; SCKL10 (617253), caused by mutation in the NSMCE2 gene (617246) on chromosome 8q24; and SCKL11 (620767), caused by mutation in the CEP295 gene (617728) on chromosome 11q21. The report of a Seckel syndrome locus on chromosome 14q, designated SCKL3, by Kilinc et al. (2003) was found to be in error; see History section.

Autosomal dominant Robinow syndrome (ADRS) is characterized by skeletal findings (short stature, mesomelic limb shortening predominantly of the upper limbs, and brachydactyly), genital abnormalities (in males: micropenis / webbed penis, hypoplastic scrotum, cryptorchidism; in females: hypoplastic clitoris and labia majora), dysmorphic facial features (widely spaced and prominent eyes, frontal bossing, anteverted nares, midface retrusion), dental abnormalities (including malocclusion, crowding, hypodontia, late eruption of permanent teeth), bilobed tongue, and occasional prenatal macrocephaly that persists postnatally. Less common findings include renal anomalies, radial head dislocation, vertebral abnormalities such as hemivertebrae and scoliosis, nail dysplasia, cardiac defects, cleft lip/palate, and (rarely) cognitive delay. When present, cardiac defects are a major cause of morbidity and mortality. A variant of Robinow syndrome, associated with osteosclerosis and caused by a heterozygous pathogenic variant in DVL1, is characterized by normal stature, persistent macrocephaly, increased bone mineral density with skull osteosclerosis, and hearing loss, in addition to the typical features described above.

Schwartz-Jampel syndrome type 1 (SJS1) is a rare autosomal recessive disorder characterized by muscle stiffness (myotonia) and chondrodysplasia. Affected individuals usually present in childhood with permanent muscle stiffness or bone deformities. Common clinical features include mask-like facies (narrow palpebral fissures, blepharospasm, and pursed lips); permanent muscle stiffness with continuous skeletal muscle activity recorded on electromyography; dwarfism; pectus carinatum; kyphoscoliosis; bowing of long bones; and epiphyseal, metaphyseal, and hip dysplasia. The disorder is slowly progressive but does not appear to alter life span (summary by Stum et al., 2006).

Cornelia de Lange syndrome (CdLS) encompasses a spectrum of findings from mild to severe. Severe (classic) CdLS is characterized by distinctive facial features, growth restriction (prenatal onset; <5th centile throughout life), hypertrichosis, and upper-limb reduction defects that range from subtle phalangeal abnormalities to oligodactyly (missing digits). Craniofacial features include synophrys, highly arched and/or thick eyebrows, long eyelashes, short nasal bridge with anteverted nares, small widely spaced teeth, and microcephaly. Individuals with a milder phenotype have less severe growth, cognitive, and limb involvement, but often have facial features consistent with CdLS. Across the CdLS spectrum IQ ranges from below 30 to 102 (mean: 53). Many individuals demonstrate autistic and self-destructive tendencies. Other frequent findings include cardiac septal defects, gastrointestinal dysfunction, hearing loss, myopia, and cryptorchidism or hypoplastic genitalia.

Rubinstein-Taybi syndrome (RSTS) is characterized by distinctive facial features, broad and often angulated thumbs and halluces, short stature, and moderate-to-severe intellectual disability. The characteristic craniofacial features are downslanted palpebral fissures, low-hanging columella, high palate, grimacing smile, and talon cusps. Prenatal growth is often normal, then height, weight, and head circumference percentiles rapidly drop in the first few months of life. Short stature is typical in adulthood. Obesity may develop in childhood or adolescence. Average IQ ranges between 35 and 50; however, developmental outcome varies considerably. Some individuals with EP300-RSTS have normal intellect. Additional features include ocular abnormalities, hearing loss, respiratory difficulties, congenital heart defects, renal abnormalities, cryptorchidism, feeding problems, recurrent infections, and severe constipation.

The Meier-Gorlin syndrome is a rare disorder characterized by severe intrauterine and postnatal growth retardation, microcephaly, bilateral microtia, and aplasia or hypoplasia of the patellae (summary by Shalev and Hall, 2003). While almost all cases have primordial dwarfism with substantial prenatal and postnatal growth retardation, not all cases have microcephaly, and microtia and absent/hypoplastic patella are absent in some. Despite the presence of microcephaly, intellect is usually normal (Bicknell et al., 2011). Genetic Heterogeneity of Meier-Gorlin Syndrome Most forms of Meier-Gorlin syndrome are autosomal recessive disorders, including Meier-Gorlin syndrome-1; Meier-Gorlin syndrome-2 (613800), caused by mutation in the ORC4 gene (603056) on chromosome 2q23; Meier-Gorlin syndrome-3 (613803), caused by mutation in the ORC6 gene (607213) on chromosome 16q11; Meier-Gorlin syndrome-4 (613804), caused by mutation in the CDT1 gene (605525) on chromosome 16q24; Meier-Gorlin syndrome-5 (613805), caused by mutation in the CDC6 gene (602627) on chromosome 17q21; Meier-Gorlin syndrome-7 (617063), caused by mutation in the CDC45L gene (603465) on chromosome 22q11; and Meier-Gorlin syndrome-8 (617564), caused by mutation in the MCM5 gene (602696) on chromosome 22q12. An autosomal dominant form of the disorder, Meier-Gorlin syndrome-6 (616835), is caused by mutation in the GMNN gene (602842) on chromosome 6p22.

Shwachman-Diamond syndrome (SDS) is characterized by: exocrine pancreatic dysfunction with malabsorption, malnutrition, and growth failure; hematologic abnormalities with single- or multilineage cytopenias and susceptibility to myelodysplasia syndrome (MDS) and acute myelogeneous leukemia (AML); and bone abnormalities. In almost all affected children, persistent or intermittent neutropenia is a common presenting finding, often before the diagnosis of SDS is made. Short stature and recurrent infections are common.

Spondyloepimetaphyseal dysplasia of the Di Rocco type (SEMDDR) is characterized by short stature, joint pain, and genu varum, as well as SEMD involving primarily the hips but also affecting the wrists, hands, knees, and ankles. Patients also exhibit variable degrees of metaphyseal and spine involvement (Di Rocco et al., 2018).

Ververi-Brady syndrome (VEBRAS) is characterized by mild developmental delay, mildly impaired intellectual development and speech delay, and mild dysmorphic facial features. Affected individuals can usually attend mainstream schools with support, and may also show autistic features (summary by Ververi et al., 2018).

A rare genetic endocrine growth disease resulting from growth hormone secretagogue receptor (GHSR) deficiency. The disease has characteristics of postnatal growth delay that results in short stature. The pituitary gland is typically without morphological changes, although anterior pituitary gland hypoplasia has been reported.

Zellweger spectrum disorder (ZSD) is a phenotypic continuum ranging from severe to mild. While individual phenotypes (e.g., Zellweger syndrome [ZS], neonatal adrenoleukodystrophy [NALD], and infantile Refsum disease [IRD]) were described in the past before the biochemical and molecular bases of this spectrum were fully determined, the term "ZSD" is now used to refer to all individuals with a defect in one of the ZSD-PEX genes regardless of phenotype. Individuals with ZSD usually come to clinical attention in the newborn period or later in childhood. Affected newborns are hypotonic and feed poorly. They have distinctive facies, congenital malformations (neuronal migration defects associated with neonatal-onset seizures, renal cysts, and bony stippling [chondrodysplasia punctata] of the patella[e] and the long bones), and liver disease that can be severe. Infants with severe ZSD are significantly impaired and typically die during the first year of life, usually having made no developmental progress. Individuals with intermediate/milder ZSD do not have congenital malformations, but rather progressive peroxisome dysfunction variably manifest as sensory loss (secondary to retinal dystrophy and sensorineural hearing loss), neurologic involvement (ataxia, polyneuropathy, and leukodystrophy), liver dysfunction, adrenal insufficiency, and renal oxalate stones. While hypotonia and developmental delays are typical, intellect can be normal. Some have osteopenia; almost all have ameleogenesis imperfecta in the secondary teeth.

Isolated growth hormone deficiency type IV (IGHD4) is an autosomal recessive disorder characterized by early and severe growth failure (height SDS up to -7.4), a blunted growth hormone (GH) response to different provocation tests and low insulin-like growth factor-I (IGF1; 147440) and IGF-binding protein-3 (IGFBP3; 146732) concentrations, and a good response to growth hormone treatment (summary by Alatzoglou et al., 2014). For general phenotypic information and a discussion of genetic heterogeneity of IGHD, see 262400.

Ovarian dysgenesis-7 (ODG7) is characterized by primary amenorrhea, delayed puberty, elevated gonadotropic hormones, and small uterus and ovaries. Ovarian histology shows fibrotic ovaries without follicles (Chen et al., 2018). For a discussion of genetic heterogeneity of ovarian dysgenesis, see ODG1 (233300).

Combined pituitary hormone deficiency (CPHD) in man denotes impaired production of growth hormone (GH; 139250) and one or more of the other 5 anterior pituitary hormones. Some patients exhibit only GH deficiency, although approximately 50% of isolated GH deficiency progresses to CPHD (Gergics et al., 2021). Individuals with CPHD7 have been reported with isolated GH deficiency as well as combined deficiencies including thyroid-stimulating hormone (TSH; see 188540) and/or prolactin (PRL; 176760). In addition to severe postnatal short stature, patients exhibit delayed bone age and hypoplasia of the anterior pituitary, as well as distinctive facial dysmorphisms including frontal bossing and depressed nasal bridge (Argente et al., 2014; Verberne et al., 2020; Yamada et al., 2021). For general phenotypic information and a discussion of genetic heterogeneity of CPHD, see 613038.

CAFDADD is a multisystemic developmental disorder with variable cardiac and digital anomalies and facial dysmorphism. Some patients may have seizures and ocular/aural abnormalities (Tokita et al., 2018).

Bone marrow failure syndrome-5 (BMFS5) is a hematologic disorder characterized by infantile onset of severe red cell anemia requiring transfusion. Additional features include hypogammaglobulinemia, poor growth with microcephaly, developmental delay, and seizures (summary by Toki et al., 2018) For a discussion of genetic heterogeneity of BMFS, see BMFS1 (614675).

Alpha-thalassemia X-linked intellectual disability (ATR-X) syndrome is characterized by distinctive craniofacial features, genital anomalies, hypotonia, and mild-to-profound developmental delay / intellectual disability (DD/ID). Craniofacial abnormalities include small head circumference, telecanthus or widely spaced eyes, short triangular nose, tented upper lip, and thick or everted lower lip with coarsening of the facial features over time. While all affected individuals have a normal 46,XY karyotype, genital anomalies comprise a range from hypospadias and undescended testicles, to severe hypospadias and ambiguous genitalia, to normal-appearing female external genitalia. Alpha-thalassemia, observed in about 75% of affected individuals, is mild and typically does not require treatment. Osteosarcoma has been reported in a few males with germline pathogenic variants.

Galloway-Mowat syndrome is a phenotypically heterogeneous disorder characterized by neurodevelopmental defects combined with renal-glomerular disease manifest as nephrotic syndrome and proteinuria. Most patients with GAMOS6 also have growth deficiency with variable microcephaly, and the renal disease may be age-dependent. Additional variable endocrine abnormalities have also been reported (summary by Braun et al., 2018). For a general phenotypic description and a discussion of genetic heterogeneity of GAMOS, see GAMOS1 (251300).

Turnpenny-Fry syndrome (TPFS) is characterized by developmental delay, impaired intellectual development, impaired growth, and recognizable facial features that include frontal bossing, sparse hair, malar hypoplasia, small palpebral fissures and oral stoma, and dysplastic 'satyr' ears. Other common findings include feeding problems, constipation, and a range of brain, cardiac, vascular, and skeletal malformations (Turnpenny et al., 2018).

Developmental and epileptic encephalopathy-73 (DEE73) is a neurologic disorder characterized by the onset of refractory seizures in the first months of life. Affected individuals meet almost no developmental milestones: they have hypotonia and are unable to walk, speak, or feed properly. They have poor overall growth with small head circumference and dysmorphic facial features. Additional manifestations include cortical visual impairment with roving eye movements and variable hearing loss (summary by Edvardson et al., 2019). For a general phenotypic description and a discussion of genetic heterogeneity of DEE, see 308350.

Myoectodermal gonadal dysgenesis syndrome (MEGD) is characterized by 46,XY complete or partial gonadal dysgenesis, or 46,XX gonadal dysgenesis, in association with extragonadal anomalies, including low birth weight, typical facies, rod and cone dystrophy, sensorineural hearing loss, omphalocele, anal atresia, renal agenesis, skeletal abnormalities, dry and scaly skin, severe myopathy, and neuromotor delay. Dysmorphic facial features along with muscular habitus are the hallmarks of the syndrome. Abnormal hair patterning with frontal upsweep and additional whorls, eyebrow abnormalities comprising broad, arched, and sparse or thick eyebrows, underdeveloped alae nasi, smooth philtrum, and low-set ears with overfolded helices facilitate a gestalt diagnosis. (Guran et al., 2019; Altunoglu et al., 2022).

Oculoskeletodental syndrome (OCSKD) is characterized by congenital cataract, short stature and various skeletal anomalies, dysmorphic facial features and dental anomalies, developmental delay, and stroke. Other recurrent features include hearing loss, secondary glaucoma, and nephrocalcinosis (Tiosano et al., 2019).

Rothmund-Thomson syndrome (RTS) is characterized by a rash that progresses to poikiloderma; sparse hair, eyelashes, and/or eyebrows; small size; skeletal and dental abnormalities; juvenile cataracts; and an increased risk for cancer, especially osteosarcoma. A variety of benign and malignant hematologic abnormalities have been reported in affected individuals. The rash of RTS typically develops between ages three and six months (occasionally as late as age two years) as erythema, swelling, and blistering on the face, subsequently spreading to the buttocks and extremities. The rash evolves over months to years into the chronic pattern of reticulated hypo- and hyperpigmentation, telangiectasias, and punctate atrophy (collectively known as poikiloderma) that persist throughout life. Hyperkeratotic lesions occur in approximately one third of individuals. Skeletal abnormalities can include radial ray defects, ulnar defects, absent or hypoplastic patella, and osteopenia.

De Barsy syndrome, or autosomal recessive cutis laxa type III (ARCL3), is characterized by cutis laxa, a progeria-like appearance, and ophthalmologic abnormalities (summary by Kivuva et al., 2008). For a phenotypic description and a discussion of genetic heterogeneity of autosomal recessive cutis laxa, see 219100. Genetic Heterogeneity of de Barsy Syndrome Also see ARCL3B (614438), caused by mutation in the PYCR1 gene (179035) on chromosome 17q25.

Silver-Russell Syndrome (SRS) is typically characterized by asymmetric gestational growth restriction resulting in affected individuals being born small for gestational age, with relative macrocephaly at birth (head circumference =1.5 SD above birth weight and/or length), prominent forehead usually with frontal bossing, and frequently body asymmetry. This is followed by postnatal growth failure, and in some cases progressive limb length discrepancy and feeding difficulties. Additional clinical features include triangular facies, fifth-finger clinodactyly, and micrognathia with narrow chin. Except for the limb length asymmetry, the growth failure is proportionate and head growth normal. The average adult height in untreated individuals is ~3.1±1.4 SD below the mean. The Netchine-Harbison Clinical Scoring System (NH-CSS) is a sensitive diagnostic scoring system. Clinical diagnosis can be established in an individual who meets at least four of the NH-CSS clinical criteria – prominent forehead/frontal bossing and relative macrocephaly at birth plus two additional findings – and in whom other disorders have been ruled out.

Silver-Russell Syndrome (SRS) is typically characterized by asymmetric gestational growth restriction resulting in affected individuals being born small for gestational age, with relative macrocephaly at birth (head circumference =1.5 SD above birth weight and/or length), prominent forehead usually with frontal bossing, and frequently body asymmetry. This is followed by postnatal growth failure, and in some cases progressive limb length discrepancy and feeding difficulties. Additional clinical features include triangular facies, fifth-finger clinodactyly, and micrognathia with narrow chin. Except for the limb length asymmetry, the growth failure is proportionate and head growth normal. The average adult height in untreated individuals is ~3.1±1.4 SD below the mean. The Netchine-Harbison Clinical Scoring System (NH-CSS) is a sensitive diagnostic scoring system. Clinical diagnosis can be established in an individual who meets at least four of the NH-CSS clinical criteria – prominent forehead/frontal bossing and relative macrocephaly at birth plus two additional findings – and in whom other disorders have been ruled out.

Silver-Russell Syndrome (SRS) is typically characterized by asymmetric gestational growth restriction resulting in affected individuals being born small for gestational age, with relative macrocephaly at birth (head circumference =1.5 SD above birth weight and/or length), prominent forehead usually with frontal bossing, and frequently body asymmetry. This is followed by postnatal growth failure, and in some cases progressive limb length discrepancy and feeding difficulties. Additional clinical features include triangular facies, fifth-finger clinodactyly, and micrognathia with narrow chin. Except for the limb length asymmetry, the growth failure is proportionate and head growth normal. The average adult height in untreated individuals is ~3.1±1.4 SD below the mean. The Netchine-Harbison Clinical Scoring System (NH-CSS) is a sensitive diagnostic scoring system. Clinical diagnosis can be established in an individual who meets at least four of the NH-CSS clinical criteria – prominent forehead/frontal bossing and relative macrocephaly at birth plus two additional findings – and in whom other disorders have been ruled out.

ROR2-related Robinow syndrome is characterized by distinctive craniofacial features, skeletal abnormalities, and other anomalies. Craniofacial features include macrocephaly, broad prominent forehead, low-set ears, ocular hypertelorism, prominent eyes, midface hypoplasia, short upturned nose with depressed nasal bridge and flared nostrils, large and triangular mouth with exposed incisors and upper gums, gum hypertrophy, misaligned teeth, ankyloglossia, and micrognathia. Skeletal abnormalities include short stature, mesomelic or acromesomelic limb shortening, hemivertebrae with fusion of thoracic vertebrae, and brachydactyly. Other common features include micropenis with or without cryptorchidism in males and reduced clitoral size and hypoplasia of the labia majora in females, renal tract abnormalities, and nail hypoplasia or dystrophy. The disorder is recognizable at birth or in early childhood.

Rajab interstitial lung disease with brain calcifications-1 (RILDBC1) is an autosomal recessive multisystem disorder with a highly variable phenotype. Most patients present in infancy or early childhood with poor growth and interstitial lung disease, which may lead to death. Some may also have liver, skeletal, and renal abnormalities, and most have intracranial calcifications on brain imaging. Some may have early impaired motor development, but most have normal cognitive development (summary by Xu et al., 2018). Genetic Heterogeneity of Rajab Interstitial Lung Disease with Brain Calcifications Also see Rajab interstitial disease with brain calcifications-2 (RILDBC2; 619013), caused by mutation in the FARSA gene (602918).

Autosomal dominant growth hormone insensitivity syndrome with immune dysregulation-2 (GHISID2) is a congenital disorder characterized by short stature due to insensitivity to growth hormone (GH1; 139250). Affected individuals usually have delayed bone age, delayed puberty, and decreased serum IGF1 (147440). Some patients may have features of mild immune dysregulation, such as eczema, increased serum IgE, asthma, or celiac disease (summary by Klammt et al., 2018).

DEEAH syndrome is an autosomal recessive multisystemic disorder with onset in early infancy. Affected individuals usually present in the perinatal period with respiratory insufficiency, apneic episodes, and generalized hypotonia. The patients have failure to thrive and severely impaired global development with poor acquisition of motor, cognitive, and language skills. Other common features include endocrine, pancreatic exocrine, and autonomic dysfunction, as well as hematologic disturbances, mainly low hemoglobin. Patients also have dysmorphic and myopathic facial features. Additional more variable features include seizures, undescended testes, and distal skeletal anomalies. Death in early childhood may occur (summary by Schneeberger et al., 2020).

Mitochondrial complex IV deficiency nuclear type 16 (MC4DN16) is an autosomal recessive metabolic disorder with highly variable manifestations. Common features include failure to thrive with poor overall growth, short stature, and microcephaly. Some patients additionally have neurologic involvement, including developmental regression with severe hypotonia, feeding difficulties, and seizures. Brain imaging in the more severely affected patients shows cerebral and cerebellar atrophy and abnormal lesions in the basal ganglia. In all cases, patient tissues show variably decreased levels and activity of mitochondrial respiratory complex IV (summary by Pillai et al., 2019). For a discussion of genetic heterogeneity of mitochondrial complex IV (cytochrome c oxidase) deficiency, see 220110.

Blepharophimosis-impaired intellectual development syndrome (BIS) is a congenital disorder characterized by a distinct facial appearance with blepharophimosis and global development delay. Affected individuals have delayed motor skills, sometimes with inability to walk, and impaired intellectual development with poor or absent speech; some patients show behavioral abnormalities. There are recognizable facial features, including epicanthal folds, sparse eyebrows, broad nasal bridge, short nose with downturned tip, and open mouth with thin upper lip. Other more variable features include distal skeletal anomalies, feeding difficulties with poor growth, respiratory infections, and hypotonia with peripheral spasticity (summary by Cappuccio et al., 2020).

Infantile-onset progressive leukoencephalopathy with or without deafness (LEPID) is an autosomal recessive complex neurodegenerative disorder with onset of symptoms in infancy or early childhood. Most patients present with sensorineural deafness or hypoacousia and global developmental delay. Affected individuals show episodic regression with progressive motor deterioration resulting in spastic tetraplegia and loss of ambulation, as well as impaired intellectual development with poor or absent speech. Additional more variable features may include poor overall growth with microcephaly, seizures, visual loss, microcytic anemia, and hepatic enlargement or abnormal liver enzymes. Brain imaging shows deep white matter abnormalities consistent with a progressive leukoencephalopathy. The brain and spinal cord are usually both involved; calcifications of these regions are often observed. Laboratory studies show increased serum lactate and deficiencies of mitochondrial respiratory chain complexes, consistent with global mitochondrial dysfunction. Early death often occurs (summary by Itoh et al., 2019).

SHILCA is characterized by early-onset retinal degeneration in association with sensorineural hearing loss, short stature, vertebral anomalies, and epiphyseal dysplasia, as well as motor and intellectual delay. Delayed myelination, leukoencephalopathy, and hypoplasia of the corpus callosum and cerebellum have been observed on brain MRI (Bedoni et al., 2020).

Neurodevelopmental disorder with hypotonia, facial dysmorphism, and brain abnormalities (NEDHFBA) is an autosomal recessive neurologic syndrome characterized by global developmental delay with severely impaired intellectual development, hypotonia and muscle weakness, often resulting in the inability to walk or sit, and characteristic coarse facial features. Additional features include feeding difficulties, respiratory distress, scoliosis, poor visual function, and rotary nystagmus. Brain imaging shows variable abnormalities, including enlarged ventricles, decreased white matter volume, white matter changes, thin corpus callosum, and cerebellar hypoplasia (summary by Loddo et al., 2020).

DEGCAGS syndrome is an autosomal recessive syndromic neurodevelopmental disorder characterized by global developmental delay, coarse and dysmorphic facial features, and poor growth and feeding apparent from infancy. Affected individuals have variable systemic manifestations often with significant structural defects of the cardiovascular, genitourinary, gastrointestinal, and/or skeletal systems. Additional features may include sensorineural hearing loss, hypotonia, anemia or pancytopenia, and immunodeficiency with recurrent infections. Death in childhood may occur (summary by Bertoli-Avella et al., 2021).

Chopra-Amiel-Gordon syndrome (CAGS) is an autosomal dominant disorder characterized by developmental delay and/or impaired intellectual development, speech delay, facial dysmorphism, and variable other features, including recurrent bacterial infections, ophthalmologic abnormalities, and nonspecific brain abnormalities (Chopra et al., 2021).

Developmental delay, hypotonia, musculoskeletal defects, and behavioral abnormalities (DEHMBA) is an early-onset neurodevelopmental disorder characterized by these features. Affected individuals also have nonspecific and variable dysmorphic facial features that do not constitute a recognizable gestalt. Although the disorder is caused by truncating mutations in the SRCAP gene as is FLHS, the DEHMBA phenotype is clinically distinguishable from FLHS by the lack of short stature, brachydactyly, and delayed bone age, as well as absence of a specific facial appearance. There are some overlapping features between the 2 disorders, mainly impaired intellectual development and speech delay (summary by Rots et al., 2021).

Spondylometaphyseal dysplasia Pagnamenta type (SMDP) is characterized by short stature and mild platyspondyly with no disproportion between the limbs. Mild metaphyseal changes are present (Pagnamenta et al., 2022).

Ovarian dysgenesis-9 (ODG9) is characterized by severe nonsyndromic primary ovarian insufficiency with primary amenorrhea, hypoplastic or absent ovaries, and delayed bone age. Patient cells show evidence of chromosomal instability (Smirin-Yosef et al., 2017; Heddar et al., 2022). For a general phenotypic description and discussion of genetic heterogeneity of ovarian dysgenesis, see ODG1 (233300).

Microcephaly, congenital cataract, and psoriasiform dermatitis (MCCPD) represents an inborn error of cholesterol metabolism that is characterized by accumulation of a large amount of methylsterols, particularly dimethylsterols, in affected patients. The associated features of immune dysregulation, skin disease, and growth delay can be at least partially corrected with cholesterol and statin supplements (He et al., 2014).

Orofaciodigital syndrome XVIII (OFD18) is characterized by short stature, brachymesophalangy, pre- and postaxial polysyndactyly, and stocky femoral necks, as well as oral anomalies and dysmorphic facial features (Thevenon et al., 2016).

A rare genetic multiple congenital anomalies/dysmorphic syndrome with characteristics of global developmental delay and intellectual disability, progressive spondyloepimetaphyseal dysplasia, short stature, short fourth metatarsals and dysmorphic craniofacial features (including microcephaly, hypertelorism, epicanthal folds, mild ptosis, strabismus, malar hypoplasia, short nose, depressed nasal bridge, full lips, small, low-set ears and short neck). Craniosynostosis, generalized hypotonia, as well as asymmetry of the cerebral hemispheres and mild thinning of the corpus callosum on brain imaging have also been described.

Autosomal dominant spastic paraplegia-9A is a neurologic disorder characterized by onset of slowly progressive spasticity mainly affecting the lower limbs. The age at onset usually ranges from adolescence to adulthood, and patients have gait difficulties, motor neuropathy, and dysarthria. Additional variable features include cerebellar signs, cataract, pes cavus, and urinary urgency (summary by Coutelier et al., 2015). For a general phenotypic description and a discussion of genetic heterogeneity of autosomal dominant spastic paraplegia, see SPG3A (182600).

Congenital idiopathic hypogonadotropic hypogonadism (IHH) is a disorder characterized by absent or incomplete sexual maturation by the age of 18 years, in conjunction with low levels of circulating gonadotropins and testosterone and no other abnormalities of the hypothalamic-pituitary axis. Idiopathic hypogonadotropic hypogonadism can be caused by an isolated defect in gonadotropin-releasing hormone (GNRH; 152760) release, action, or both. Other associated nonreproductive phenotypes, such as anosmia, cleft palate, and sensorineural hearing loss, occur with variable frequency. In the presence of anosmia, idiopathic hypogonadotropic hypogonadism has been called 'Kallmann syndrome (KS),' whereas in the presence of a normal sense of smell, it has been termed 'normosmic idiopathic hypogonadotropic hypogonadism (nIHH)' (summary by Raivio et al., 2007). Because families have been found to segregate both KS and nIHH, the disorder is here referred to as 'hypogonadotropic hypogonadism with or without anosmia (HH).' For a general phenotypic description and a discussion of genetic heterogeneity of hypogonadotropic hypogonadism with or without anosmia, see 147950.

Abnormal thyroid hormone metabolism-1 (THMA1) is characterized by multiorgan defects, including abnormal thyroid hormone metabolism, myopathy, hearing loss, and male infertility (summary by Catli et al., 2018). Genetic Heterogeneity of Abnormal Thyroid Hormone Metabolism THMA2 (619855) is caused by mutation in the DIO1 gene (147892) on chromosome 1p32. THMA3 (620198) is caused by mutation in the TRU-TCA1-1 gene (165060) on chromosome 19q13.

Congenital disorder of glycosylation type IIy (CDG2Y) is an autosomal recessive multisystemic congenital disorder characterized by poor overall growth and global developmental delay with impaired intellectual development. Other features may include hypotonia, seizures, brain imaging abnormalities, dysmorphic features, and various skeletal defects. Laboratory studies show a subtle type II glycosylation defect of serum transferrin (Tambe et al., 2020). For a general discussion of CDGs, see CDG1A (212065).

Autosomal recessive intellectual developmental disorder-78 (MRT78) is a neurodevelopmental disorder characterized by impaired intellectual development that is usually mild, but shows variable severity. Affected individuals have microcephaly and mild short stature. Additional features may include ocular abnormalities and mild skeletal defects (Haag et al., 2021).

Autosomal dominant intellectual developmental disorder-73 (MRD73) is a highly variable neurodevelopmental disorder characterized by impaired intellectual development that ranges from mild to severe, speech delay, behavioral abnormalities, and nonspecific dysmorphic facial features (Janssen et al., 2022).

Childhood-onset variegate porphyria (VPCO), also called 'homozygous' variegate porphyria, is a rare disorder of heme biosynthesis characterized by severe PPOX deficiency, onset of photosensitization by porphyrins in early childhood, skeletal abnormalities of the hand, and, less consistently, short stature, impaired intellectual development, and seizures. The term 'homozygous' refers to the presence of mutations on both alleles of the PPOX gene, resulting in earlier onset and more severe manifestations than those seen in variegate porphyria (VP), a low-penetrance disorder inherited as an autosomal dominant trait (summary by Roberts et al., 1998). Heterozygous family members of VPCO patients are usually clinically silent, but symptomatic heterozygotes have been reported (Mustajoki et al., 1987; Palmer et al., 2001; Kauppinen et al., 2001). Nomenclature 'Homozygous' variegate porphyria was so designated before the molecular defect in PPOX was elucidated, on the basis of severe reduction in PPOX activity (between 5 and 20% of control values) compared to that seen in variegate porphyria (approximately 50% reduction), in which autosomal dominant transmission had been observed. It is probable that most cases of 'homozygous' variegate porphyria actually result from compound heterozygosity for PPOX mutations (Frank et al., 1998; Palmer et al., 2001).

Ziegler-Huang syndrome (ZHS) is a bone marrow failure syndrome characterized by severe growth retardation responsive to growth hormone (GH1; 139250) treatment, testicular hypoplasia, and progressive bone marrow failure, with thrombocytopenia and macrocytosis developing in childhood (Huang et al., 2023). For a general phenotypic description and discussion of genetic heterogeneity of bone marrow failure syndromes, see BMFS1 (614675).

Cornelia de Lange syndrome (CDLS) is a genetically heterogeneous developmental disorder characterized by malformations affecting multiple systems. Affected individuals have dysmorphic facial features, cleft palate, distal limb defects, growth retardation, and developmental delay. About 60% of patients have mutations in the NIPBL gene (608667) (summary by Musio et al., 2006 and Hoppman-Chaney et al., 2012). For a general phenotypic description and a discussion of genetic heterogeneity of Cornelia de Lange syndrome, see CDLS1 (122470).

Hoxha-Aliu syndrome (HXAL) is characterized by mildly impaired intellectual development and digital anomalies of the hands and feet (Hoxha and Aliu, 2023; Guo et al., 2023). Biallelic missense mutations in the ERI1 gene have been reported to cause a more severe bone disorder, spondyloepimetaphyseal dysplasia, Guo-Campeau type (SEMDGC; 620663).

The Guo-Campeau type of spondyloepimetaphyseal dysplasia (SEMDGC) is characterized by severe bone dysplasia resulting in significant short stature with variable anomalies of the spine, pelvis, hips, and extremities, including short, rudimentary, or absent digits. Patients also exhibit variable facial dysmorphisms (Guo et al., 2023). Biallelic null mutations in the ERI1 gene have been reported to cause a less severe disorder, Hoxha-Alia syndrome, involving digital anomalies and mild intellectual disability (HXAL; 620662).

Autosomal recessive intellectual developmental disorder-81 (MRT81) is characterized by a variable neurobehavioral and neuromuscular phenotype (summary by Nair et al., 2021).