Cystic fibrosis (CF) is a multisystem disease affecting epithelia of the respiratory tract, exocrine pancreas, intestine, hepatobiliary system, and exocrine sweat glands. Morbidities include recurrent sinusitis and bronchitis, progressive obstructive pulmonary disease with bronchiectasis, exocrine pancreatic deficiency and malnutrition, pancreatitis, gastrointestinal manifestations (meconium ileus, rectal prolapse, distal intestinal obstructive syndrome), liver disease, diabetes, male infertility due to hypoplasia or aplasia of the vas deferens, and reduced fertility or infertility in some women. Pulmonary disease is the major cause of morbidity and mortality in CF.

Individuals with 22q11.2 deletion syndrome (22q11.2DS) can present with a wide range of features that are highly variable, even within families. The major clinical manifestations of 22q11.2DS include congenital heart disease, particularly conotruncal malformations (ventricular septal defect, tetralogy of Fallot, interrupted aortic arch, and truncus arteriosus), palatal abnormalities (velopharyngeal incompetence, submucosal cleft palate, bifid uvula, and cleft palate), immune deficiency, characteristic facial features, and learning difficulties. Hearing loss can be sensorineural and/or conductive. Laryngotracheoesophageal, gastrointestinal, ophthalmologic, central nervous system, skeletal, and genitourinary anomalies also occur. Psychiatric illness and autoimmune disorders are more common in individuals with 22q11.2DS.

Mucopolysaccharidosis type II (MPS II; also known as Hunter syndrome) is an X-linked multisystem disorder characterized by glycosaminoglycan (GAG) accumulation. The vast majority of affected individuals are male; on rare occasion heterozygous females manifest findings. Age of onset, disease severity, and rate of progression vary significantly among affected males. In those with early progressive disease, CNS involvement (manifest primarily by progressive cognitive deterioration), progressive airway disease, and cardiac disease usually result in death in the first or second decade of life. In those with slowly progressive disease, the CNS is not (or is minimally) affected, although the effect of GAG accumulation on other organ systems may be early progressive to the same degree as in those who have progressive cognitive decline. Survival into the early adult years with normal intelligence is common in the slowly progressing form of the disease. Additional findings in both forms of MPS II include: short stature; macrocephaly with or without communicating hydrocephalus; macroglossia; hoarse voice; conductive and sensorineural hearing loss; hepatosplenomegaly; dysostosis multiplex; spinal stenosis; and carpal tunnel syndrome.

The phenotypic characteristics of ichthyosis vulgaris include palmar hyperlinearity, keratosis pilaris, and a fine scale that is most prominent over the lower abdomen, arms, and legs. Marked presentation includes prominent scaling, whereas mild presentation consists of palmar hyperlinearity, keratosis pilaris, and, in some cases, fine scaling (summary by Smith et al., 2006).

Alström syndrome is characterized by cone-rod dystrophy, obesity, progressive bilateral sensorineural hearing impairment, acute infantile-onset cardiomyopathy and/or adolescent- or adult-onset restrictive cardiomyopathy, insulin resistance / type 2 diabetes mellitus (T2DM), nonalcoholic fatty liver disease (NAFLD), and chronic progressive kidney disease. Cone-rod dystrophy presents as progressive visual impairment, photophobia, and nystagmus usually starting between birth and age 15 months. Many individuals lose all perception of light by the end of the second decade, but a minority retain the ability to read large print into the third decade. Children usually have normal birth weight but develop truncal obesity during their first year. Sensorineural hearing loss presents in the first decade in as many as 70% of individuals and may progress to the severe or moderately severe range (40-70 db) by the end of the first to second decade. Insulin resistance is typically accompanied by the skin changes of acanthosis nigricans, and proceeds to T2DM in the majority by the third decade. Nearly all demonstrate hypertriglyceridemia. Other findings can include endocrine abnormalities (hypothyroidism, hypogonadotropic hypogonadism in males, and hyperandrogenism in females), urologic dysfunction / detrusor instability, progressive decrease in renal function, and hepatic disease (ranging from elevated transaminases to steatohepatitis/NAFLD). Approximately 20% of affected individuals have delay in early developmental milestones, most commonly in gross and fine motor skills. About 30% have a learning disability. Cognitive impairment (IQ <70) is very rare. Wide clinical variability is observed among affected individuals, even within the same family.

Level of glutathione in the urine above the upper limit of normal.

Prolidase deficiency is characterized by skin lesions (typically severe, chronic, recalcitrant, and painful skin ulcers of the lower extremities and telangiectasias of the face and hands), recurrent infections (particularly of the skin and respiratory tract), dysmorphic facial features, variable intellectual disability, and organomegaly (typically splenomegaly but occasionally associated with hepatomegaly) with elevated liver enzymes. Skeletal anomalies, chronic pulmonary disease, anemia, thrombocytopenia, hypergammaglobulinemia, and hypocomplementemia are observed in a minority of affected individuals. An association between prolidase deficiency and autoimmune conditions – particularly systemic lupus erythematosus (SLE) – has been described.

Monosomy 18q is a partial deletion of the long arm of chromosome 18 characterized by highly variable phenotype, most commonly including hypotonia, developmental delay, short stature, growth hormone deficiency, hearing loss and external ear anomalies, intellectual disability, palatal defects, dysmorphic facial features, skeletal anomalies (foot deformities, tapering fingers, scoliosis) and mood disorders.

Transaldolase deficiency (TALDOD) is a rare inborn error of pentose metabolism. Typical features include intrauterine growth restriction, triangular face, loose wrinkly skin at birth, and development of progressive liver failure (summary by Lee-Barber et al., 2019).

Autosomal recessive congenital ichthyosis (ARCI) encompasses several forms of nonsyndromic ichthyosis. Although most neonates with ARCI are collodion babies, the clinical presentation and severity of ARCI may vary significantly, ranging from harlequin ichthyosis, the most severe and often fatal form, to lamellar ichthyosis (LI) and (nonbullous) congenital ichthyosiform erythroderma (CIE). These phenotypes are now recognized to fall on a continuum; however, the phenotypic descriptions are clinically useful for clarification of prognosis and management. Infants with harlequin ichthyosis are usually born prematurely and are encased in thick, hard, armor-like plates of cornified skin that severely restrict movement. Life-threatening complications in the immediate postnatal period include respiratory distress, feeding problems, and systemic infection. Collodion babies are born with a taut, shiny, translucent or opaque membrane that encases the entire body and lasts for days to weeks. LI and CIE are seemingly distinct phenotypes: classic, severe LI with dark brown, plate-like scale with no erythroderma and CIE with finer whiter scale and underlying generalized redness of the skin. Affected individuals with severe involvement can have ectropion, eclabium, scarring alopecia involving the scalp and eyebrows, and palmar and plantar keratoderma. Besides these major forms of nonsyndromic ichthyosis, a few rare subtypes have been recognized, such as bathing suit ichthyosis, self-improving collodion ichthyosis, or ichthyosis-prematurity syndrome.

Atopy is an allergic disorder characterized by immunoglobulin E (IgE) responses to environmental proteins that are otherwise innocuous and predominantly found in plant pollen and house dust. It is the major cause of asthma (see 600807), rhinitis (see 607154), and eczema (see 603165) in children and young adults (summary by Young et al., 1992).

X-linked intellectual disability-retinitis pigmentosa syndrome is characterized by moderate intellectual deficit and severe, early-onset retinitis pigmentosa. It has been described in five males spanning three generations of one family. Some patients also had microcephaly. It is transmitted as an X-linked recessive trait.

Caspase 8 deficiency is a syndrome of lymphadenopathy and splenomegaly, marginal elevation of 'double-negative T cells' (DNT; T-cell receptor alpha/beta+, CD4-/CD8-), defective FAS-induced apoptosis, and defective T-, B-, and natural killer (NK)-cell activation, with recurrent bacterial and viral infections (summary by Madkaikar et al., 2011).

LIG4 syndrome is an autosomal recessive severe combined immunodeficiency with features of radiosensitivity, chromosomal instability, pancytopenia, and developmental and growth delay. Leukemia and dysmorphic facial features have been reported in some patients (summary by van der Burg et al., 2006).

A group of rare autosomal recessive forms of ichthyosis with clinical characteristics of superficial, asymptomatic, spontaneous peeling of the skin and histologically by a shedding of the outer layers of the epidermis. Presents with either an acral or a generalised distribution.

Adenosine deaminase (ADA) deficiency is a systemic purine metabolic disorder that primarily affects lymphocyte development, viability, and function. The clinical phenotypic spectrum includes: Severe combined immunodeficiency disease (SCID), often diagnosed by age six months and usually by age 12 months; Less severe "delayed" onset combined immune deficiency (CID), usually diagnosed between age one and ten years; "Late/adult onset" CID, diagnosed in the second to fourth decades; Benign "partial ADA deficiency" (very low or absent ADA activity in erythrocytes but greater ADA activity in nucleated cells), which is compatible with normal immune function. Infants with typical early-onset ADA-deficient SCID have failure to thrive and opportunistic infections associated with marked depletion of T, B, and NK lymphocytes, and an absence of both humoral and cellular immune function. If immune function is not restored, children with ADA-deficient SCID rarely survive beyond age one to two years. Infections in delayed- and late-onset types (commonly, recurrent otitis, sinusitis, and upper respiratory) may initially be less severe than those in individuals with ADA-deficient SCID; however, by the time of diagnosis these individuals often have chronic pulmonary insufficiency and may have autoimmune phenomena (cytopenias, anti-thyroid antibodies), allergies, and elevated serum concentration of IgE. The longer the disorder goes unrecognized, the more immune function deteriorates and the more likely are chronic sequelae of recurrent infection.

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\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\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\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. 

Bronchial asthma is the most common chronic disease affecting children and young adults. It is a complex genetic disorder with a heterogeneous phenotype, largely attributed to the interactions among many genes and between these genes and the environment. Asthma-related traits include clinical symptoms of asthma, such as coughing, wheezing, and dyspnea; bronchial hyperresponsiveness (BHR) as assessed by methacholine challenge test; serum IgE levels; atopy; and atopic dermatitis (Laitinen et al., 2001; Illig and Wjst, 2002; Pillai et al., 2006). See 147050 for information on the asthma-associated phenotype atopy.

NKX2-1-related disorders range from benign hereditary chorea (BHC) to choreoathetosis, congenital hypothyroidism, and neonatal respiratory distress (also known as brain-lung-thyroid syndrome). Childhood-onset chorea, the hallmark of NKX2-1-related disorders, may or may not be associated with respiratory distress syndrome or congenital hypothyroidism. Chorea generally begins in early infancy or about age one year (most commonly) or in late childhood or adolescence, and progresses into the second decade after which it remains static or (rarely) remits. Pulmonary disease, the second most common manifestation, can include respiratory distress syndrome in neonates, interstitial lung disease in young children, and pulmonary fibrosis in older persons. The risk for pulmonary carcinoma is increased in young adults with an NKX2-1-related disorder. Thyroid dysfunction, the result of dysembryogenesis, can present as congenital hypothyroidism or compensated hypothyroidism. The risk for thyroid cancer is unknown and may not be increased. In one review, 50% of affected individuals had the full brain-lung-thyroid syndrome, 30% had involvement of brain and thyroid only, and 13% had isolated chorea only.

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.

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).

Bardet-Biedl syndrome is an autosomal recessive and genetically heterogeneous ciliopathy characterized by retinitis pigmentosa, obesity, kidney dysfunction, polydactyly, behavioral dysfunction, and hypogonadism (summary by Beales et al., 1999). Eight proteins implicated in the disorder assemble to form the BBSome, a stable complex involved in signaling receptor trafficking to and from cilia (summary by Scheidecker et al., 2014). Genetic Heterogeneity of Bardet-Biedl Syndrome BBS2 (615981) is caused by mutation in a gene on 16q13 (606151); BBS3 (600151), by mutation in the ARL6 gene on 3q11 (608845); BBS4 (615982), by mutation in a gene on 15q22 (600374); BBS5 (615983), by mutation in a gene on 2q31 (603650); BBS6 (605231), by mutation in the MKKS gene on 20p12 (604896); BBS7 (615984), by mutation in a gene on 4q27 (607590); BBS8 (615985), by mutation in the TTC8 gene on 14q32 (608132); BBS9 (615986), by mutation in a gene on 7p14 (607968); BBS10 (615987), by mutation in a gene on 12q21 (610148); BBS11 (615988), by mutation in the TRIM32 gene on 9q33 (602290); BBS12 (615989), by mutation in a gene on 4q27 (610683); BBS13 (615990), by mutation in the MKS1 gene (609883) on 17q23; BBS14 (615991), by mutation in the CEP290 gene (610142) on 12q21, BBS15 (615992), by mutation in the WDPCP gene (613580) on 2p15; BBS16 (615993), by mutation in the SDCCAG8 gene (613524) on 1q43; BBS17 (615994), by mutation in the LZTFL1 gene (606568) on 3p21; BBS18 (615995), by mutation in the BBIP1 gene (613605) on 10q25; BBS19 (615996), by mutation in the IFT27 gene (615870) on 22q12; BBS20 (619471), by mutation in the IFT172 gene (607386) on 9p21; BBS21 (617406), by mutation in the CFAP418 gene (614477) on 8q22; and BBS22 (617119), by mutation in the IFT74 gene (608040) on 9p21. The CCDC28B gene (610162) modifies the expression of BBS phenotypes in patients who have mutations in other genes. Mutations in MKS1, MKS3 (TMEM67; 609884), and C2ORF86 also modify the expression of BBS phenotypes in patients who have mutations in other genes. Although BBS had originally been thought to be a recessive disorder, Katsanis et al. (2001) demonstrated that clinical manifestation of some forms of Bardet-Biedl syndrome requires recessive mutations in 1 of the 6 loci plus an additional mutation in a second locus. While Katsanis et al. (2001) called this 'triallelic inheritance,' Burghes et al. (2001) suggested the term 'recessive inheritance with a modifier of penetrance.' Mykytyn et al. (2002) found no evidence of involvement of the common BBS1 mutation in triallelic inheritance. However, Fan et al. (2004) found heterozygosity in a mutation of the BBS3 gene (608845.0002) as an apparent modifier of the expression of homozygosity of the met390-to-arg mutation in the BBS1 gene (209901.0001). Allelic disorders include nonsyndromic forms of retinitis pigmentosa: RP51 (613464), caused by TTC8 mutation, and RP55 (613575), caused by ARL6 mutation.

A heterozygous deletion of chromosome 15q11.2 may increase the susceptibility to neuropsychiatric or neurodevelopmental problems, including delayed psychomotor development, speech delay, autism spectrum disorder, attention deficit-hyperactivity disorder, obsessive-compulsive disorder, and possibly seizures (summary by Doornbos et al., 2009 and Burnside et al., 2011). See also chromosome 15q11.2 duplication syndrome (608636).

Concentration of the complement component C4b in the blood circulation below the lower limit of normal.

ISQMR is a severe autosomal recessive disorder characterized by ichthyosis apparent from birth, profound psychomotor retardation with essentially no development, spastic quadriplegia, and seizures (summary by Aldahmesh et al., 2011).

Familial cold autoinflammatory syndrome-3 is an autosomal dominant immune disorder characterized by the development of cutaneous urticaria, erythema, and pruritus in response to cold exposure. Affected individuals have variable additional immunologic defects, including antibody deficiency, decreased numbers of B cells, defective B cells, increased susceptibility to infection, and increased risk of autoimmune disorders (summary by Ombrello et al., 2012). For a discussion of genetic heterogeneity of FCAS, see FCAS1 (120100).

Common variable immunodeficiency-8 with autoimmunity is an autosomal recessive disorder of immune dysregulation. Affected individuals have early childhood onset of recurrent infections, particularly respiratory infections, and also develop variable autoimmune disorders, including idiopathic thrombocytopenic purpura, autoimmune hemolytic anemia, and inflammatory bowel disease. The presentation and phenotype are highly variable, even within families (summary by Lopez-Herrera et al., 2012 and Alangari et al., 2012). Immunologic findings are also variable and may include decreased B cells, hypogammaglobulinemia, and deficiency of CD4+ T regulatory (Treg) cells (Charbonnier et al., 2015). For a general description and a discussion of genetic heterogeneity of common variable immunodeficiency, see CVID1 (607594).

Common variable immunodeficiency-10 (CVID10) is an autosomal dominant primary immunodeficiency characterized by childhood-onset of recurrent infections, hypogammaglobulinemia, and decreased numbers of memory and marginal zone B cells. Some patients may develop autoimmune features and have circulating autoantibodies. An unusual feature is central adrenal insufficiency (summary by Chen et al., 2013). For a general description and a discussion of genetic heterogeneity of common variable immunodeficiency, see CVID1 (607594).

IMD23 is an autosomal recessive primary immunodeficiency syndrome characterized by onset of recurrent infections, usually respiratory or cutaneous, in early childhood. Immune workup usually shows neutropenia, lymphopenia, eosinophilia, and increased serum IgE or IgA. Neutrophil chemotactic defects have also been reported. Infectious agents include bacteria, viruses, and fungi. Many patients develop atopic dermatitis, eczema, and other signs of autoinflammation. Affected individuals may also show developmental delay or cognitive impairment of varying severity (summary by Bjorksten and Lundmark, 1976 and Zhang et al., 2014).

A rare genetic ectodermal dysplasia syndrome characterized by short stature, nail dystrophy and/or nail loss, oral mucosa and/or tongue hyperpigmentation, dentition abnormalities (delayed teeth eruption, hypodontia, enamel hypoplasia), keratoderma on the margins of the palms and soles and focal hyperkeratosis on the dorsum of the hands and feet. Additionally, dysphagia with esophageal strictures, sensorineural deafness, bronchial asthma and severe iron-deficiency anemia have also been observed.

Any primary ciliary dyskinesia in which the cause of the disease is a mutation in the CCDC151 gene.

DDX41-associated familial myelodysplastic syndrome and acute myeloid leukemia (MDS/AML) is characterized by an increased risk of myeloid neoplasms, lymphoid neoplasms, adult-onset single- or multiple-lineage cytopenias (including aplastic anemia), and red blood cell macrocytosis. The most common myeloid neoplasms include MDS, AML, and therapy-related myeloid neoplasms. Chronic myelomonocytic leukemia, chronic myeloid leukemia, and myeloproliferative neoplasms are less common. Lymphoid neoplasms include non-Hodgkin lymphoma, Hodgkin lymphoma, multiple myeloma, chronic lymphocytic leukemia, and acute lymphoblastic leukemia.

Any Seckel syndrome in which the cause of the disease is a mutation in the TRAIP gene.

Rhizomelic chondrodysplasia punctata (RCDP) is a peroxisomal disorder characterized by disproportionately short stature primarily affecting the proximal parts of the extremities, a typical facial appearance including a broad nasal bridge, epicanthus, high-arched palate, dysplastic external ears, and micrognathia, congenital contractures, characteristic ocular involvement, dwarfism, and severe mental retardation with spasticity. Biochemically, plasmalogen synthesis and phytanic acid alpha-oxidation are defective. Most patients die in the first decade of life (summary by Wanders and Waterham, 2005). For a discussion of genetic heterogeneity of rhizomelic chondrodysplasia punctata, see 215100.

Yao syndrome (YAOS) is an autoinflammatory disease characterized by periodic fever, dermatitis, arthritis, and swelling of the distal extremities, as well as gastrointestinal and sicca-like symptoms. The disorder is associated with specific NOD2 variants (and Shen, 2017).

Bardet-Biedl syndrome-20 (BBS20), a rare autosomal recessive disorder associated with ciliary dysfunction, is characterized by rod-cone dystrophy, postaxial polydactyly, truncal obesity, renal anomalies, and learning disability, as well as hypogonadism in males and genital abnormalities in females (Saida et al., 2014). For a general phenotypic description and discussion of genetic heterogeneity of Bardet-Biedl syndrome, see BBS1 (209900).

GNB1 encephalopathy (GNB1-E) is characterized by moderate-to-severe developmental delay / intellectual disability, structural brain abnormalities, and often infantile hypotonia and seizures. Other less common findings include dystonia, reduced vision, behavior issues, growth delay, gastrointestinal (GI) problems, genitourinary (GU) abnormalities in males, and cutaneous mastocytosis.

IMD11B is an autosomal dominant disorder of immune dysfunction characterized by onset of moderate to severe atopic dermatitis in early childhood. Some patients may have recurrent infections and other variable immune abnormalities. Laboratory studies show defects in T-cell activation, increased IgE, and eosinophilia (summary by Ma et al., 2017).

Hyper-IgE syndrome-2 with recurrent infections (HIES2) is an autosomal recessive immunologic disorder characterized by recurrent staphylococcal infections of the skin and respiratory tract, eczema, elevated serum immunoglobulin E, and hypereosinophilia. It is distinguished from autosomal dominant HIES1 (147060) by the lack of connective tissue and skeletal involvement (Renner et al., 2004). For a discussion of genetic heterogeneity of hyper-IgE syndrome, see 147060. See also TYK2 deficiency (611521), a clinically distinct disease entity that includes characteristic features of both autosomal recessive HIES2 and mendelian susceptibility to mycobacterial disease (MSMD; 209950) (Minegishi et al., 2006).

Any BAFopathy in which the cause of the disease is a mutation in the BCL11B gene.

Immunodeficiency-58 is an autosomal recessive primary immunologic disorder characterized by early-onset skin lesions, including eczematous dermatitis, infectious abscesses, and warts, recurrent respiratory infections or allergies, and chronic persistent infections with candida, Molluscum contagiosum, mycobacteria, EBV, bacteria, and viruses. Some patients may have gastrointestinal involvement, including inflammatory bowel disease, EBV+ smooth muscle tumors, and esophagitis. Immunologic analysis shows defective T-cell function with decreased Treg cells and deficient CD3/CD28 costimulation responses in both CD4+ and CD8+ T cells. B-cell function may also be impaired (summary by Wang et al., 2016 and Alazami et al., 2018).

Krakow-type spondyloepimetaphyseal dysplasia is characterized by severe skeletal dysplasia, severe immunodeficiency, and developmental delay (Csukasi et al., 2018).

Pontocerebellar hypoplasia type 13 (PCH13) is an autosomal recessive disorder characterized by global developmental delay, impaired intellectual development with absent speech, microcephaly, and progressive atrophy of the cerebellar vermis and brainstem. Additional features, including seizures and visual impairment, are variable (summary by Uwineza et al., 2019). For a general phenotypic description and a discussion of genetic heterogeneity of PCH, see PCH1A (607596).

CATIFA syndrome is characterized by global developmental delay and impaired intellectual development ranging from mild to severe, with most patients exhibiting attention-deficit hyperactivity disorder (ADHD). Patients show an elongated face with long philtrum and small ears. Ocular anomalies include congenital cataracts, strabismus, and amblyopia, which may be associated with reduced vision; other anomalies include cleft lip and/or palate and misaligned teeth with extensive caries (Unlu et al., 2020).

Autoinflammation, immune dysregulation, and eosinophilia (AIIDE) is an autosomal dominant disorder characterized by onset of severe atopic dermatitis and chronic gastrointestinal inflammation, mainly involving the colon, in infancy or early childhood. Affected individuals tend to have asthma and food or environmental allergies, as well as poor overall growth with short stature. Severe liver involvement has also been reported (Takeichi et al., 2021). Laboratory studies show increased eosinophils with normal or increased IgE levels, as well as evidence of a hyperactive immune state, including increased erythrocyte sedimentation rate and C-reactive protein. Treatment with JAK inhibitors, such as ruxolitinib and tofacitinib, results in dramatic clinical improvement (summary by Gruber et al., 2020).

Odontochondrodysplasia-2 with hearing loss and diabetes (ODCD2) is characterized by growth retardation with proportionate short stature, dentinogenesis imperfecta, sensorineural hearing loss, insulin-dependent diabetes, and mild intellectual disability (Cauwels et al., 2005; Lekszas et al., 2020). For a discussion of genetic heterogeneity of ODCD, see ODCD1 (184260).

Osteootohepatoenteric syndrome (OOHE) is characterized by a variable combination of bone fragility, hearing loss, cholestasis, and congenital diarrhea. Some patients also display mild developmental delay and intellectual disability (Esteve et al., 2018).

VISS syndrome is a generalized connective tissue disorder characterized by early-onset thoracic aortic aneurysm and other connective tissue findings, such as aneurysm and tortuosity of other arteries, joint hypermobility, skin laxity, and hernias, as well as craniofacial dysmorphic features, structural cardiac defects, skeletal anomalies, and motor developmental delay (Van Gucht et al., 2021). Immune dysregulation has been observed in some patients (Ziegler et al., 2021).

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).

Neurodevelopmental disorder with hypotonia and dysmorphic facies (NEDHYDF) is characterized by global developmental delay and hypotonia apparent from birth. Affected individuals have variably impaired intellectual development, often with speech delay and delayed walking. Seizures are generally not observed, although some patients may have single seizures or late-onset epilepsy. Most patients have prominent dysmorphic facial features. Additional features may include congenital cardiac defects (without arrhythmia), nonspecific renal anomalies, joint contractures or joint hyperextensibility, dry skin, and cryptorchidism. There is significant phenotypic variability in both the neurologic and extraneurologic manifestations (summary by Tan et al., 2022).

Biliary, renal, neurologic, and skeletal syndrome (BRENS) is an autosomal recessive complex ciliopathy with multisystemic manifestations. The most common presentation is severe neonatal cholestasis that progresses to liver fibrosis and cirrhosis. Most patients have additional clinical features suggestive of a ciliopathy, including postaxial polydactyly, hydrocephalus, retinal abnormalities, and situs inversus. Additional features of the syndrome may include congenital cardiac defects, echogenic kidneys with renal failure, ocular abnormalities, joint hyperextensibility, and dysmorphic facial features. Some patients have global developmental delay. Brain imaging typically shows dilated ventricles, hypomyelination, and white matter abnormalities, although some patients have been described with abnormal pituitary development (summary by Shaheen et al., 2020 and David et al., 2020).

Immunodeficiency-88 (IMD88) is an autosomal recessive immune disorder characterized specifically by the development of disseminated mycobacterial disease following vaccination with BCG. The single patient described did not develop other clinical infectious diseases, although serology documented exposure to various viruses and bacteria. Immunologic workup shows defective development of certain innate immunologic cells and decreased production of gamma-interferon (IFNG; 147570). Additional manifestations include persistent reactive airway disease associated with increased production of Th2 cytokines (summary by Yang et al., 2020 and Yang et al., 2021).

Immunodeficiency-89 and autoimmunity (IMD89) is an autosomal recessive immune disorder characterized by adult onset of recurrent infections, allergies, microcytic anemia, and Crohn disease (see 266600) (Yang et al., 2020).

Netherton syndrome (NETH) is a rare and severe autosomal recessive skin disorder characterized by congenital erythroderma, a specific hair-shaft abnormality, and atopic manifestations with high IgE levels. Generalized scaly erythroderma is apparent at or soon after birth and usually persists. Scalp hair is sparse and brittle with a characteristic 'bamboo' shape under light microscopic examination due to invagination of the distal part of the hair shaft to its proximal part. Atopic manifestations include eczema-like rashes, atopic dermatitis, pruritus, hay fever, angioedema, urticaria, high levels of IgE in the serum, and hypereosinophilia. Life-threatening complications are frequent during the neonatal period, including hypernatremic dehydration, hypothermia, extreme weight loss, bronchopneumonia, and sepsis. During childhood, failure to thrive is common as a result of malnutrition, metabolic disorders, chronic erythroderma, persistent cutaneous infections, or enteropathy (summary by Bitoun et al., 2002).

Immunodeficiency-94 with autoinflammation and dysmorphic facies (IMD94) is a systemic immunologic disorder with onset in early infancy. Primary features include lymphadenopathy, autoinflammation, immunodeficiency with hypogammaglobulinemia, and dysmorphic facial features. Intellectual development is normal and serum IgE is not elevated. The disease results from constitutive activation of the IL6 signaling cascade, resulting in immune dysregulation and a hyperinflammatory state (summary by Materna-Kiryluk et al., 2021).

Hyper-IgE syndrome-4A with recurrent infections (HIES4A) is an autosomal dominant immunologic disorder characterized by recurrent, mainly sinopulmonary infections associated with increased serum IgE. The phenotype is variable, even within families. Some patients have onset of symptoms in early childhood and develop complications, including bronchiectasis or hemoptysis, whereas others have later onset of less severe infections. Immunologic workup usually shows normal leukocyte levels, although some patients may demonstrate alterations in lymphocyte subsets, including T cells. Affected individuals also have variable skeletal abnormalities, including high-arched palate, hyperextensible joints, scoliosis, and bone fractures. The IL6ST mutations are loss-of-function, although the truncated mutant proteins are expressed and interfere with the wildtype protein in a dominant-negative manner by disrupting IL6 (147620) and IL11 (147681) signaling (summary by Beziat et al., 2020). For a discussion of genetic heterogeneity of hyper-IgE syndrome, see HIES1 (147060).

Chilton-Okur-Chung neurodevelopmental syndrome (CHOCNS) is characterized mainly by global developmental delay with variably impaired intellectual development and occasional speech delay. Most patients have behavioral abnormalities, including autism spectrum disorder, ADHD, and aggression. About half of patients have dysmorphic facial features, and about half have nonspecific brain abnormalities, including thin corpus callosum. Rare involvement of other organ systems may be present. At least 1 child with normal development at age 2.5 years has been reported (Chilton et al., 2020).

Recurrent respiratory infections and failure to thrive with or without diarrhea (RIFTD) is characterized by neonatal onset of chronic cough, episodic wheezing, recurrent lower respiratory tract infections, chronic diarrhea, and failure to thrive. Despite the resemblance to cystic fibrosis (CF; 219700), these patients have normal sweat chloride and pancreatic elastase tests (Bertoli-Avella et al., 2022).

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-71 with behavioral abnormalities (MRD71) is a neurodevelopmental disorder characterized by global developmental delay with hypotonia, speech delay, and variably impaired cognitive development. Almost all affected individuals show marked behavioral manifestations, including autism spectrum disorder (ASD), ADHD, hypersensitivity, and aggression. Many have dysmorphic features, although there is not a common gestalt (Harris et al., 2021).

Hatipoglu immunodeficiency syndrome (HATIS) is an autosomal recessive immunologic disorder characterized by childhood onset of failure to thrive, skin manifestations, pancytopenia, and susceptibility to recurrent infections (Harapas et al., 2022).