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1.

Mucopolysaccharidosis, MPS-II

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. [from GeneReviews]

MedGen UID:
7734
Concept ID:
C0026705
Disease or Syndrome
2.

Rett syndrome

The spectrum of MECP2-related phenotypes in females ranges from classic Rett syndrome to variant Rett syndrome with a broader clinical phenotype (either milder or more severe than classic Rett syndrome) to mild learning disabilities; the spectrum in males ranges from severe neonatal encephalopathy to pyramidal signs, parkinsonism, and macroorchidism (PPM-X) syndrome to severe syndromic/nonsyndromic intellectual disability. Females: Classic Rett syndrome, a progressive neurodevelopmental disorder primarily affecting girls, is characterized by apparently normal psychomotor development during the first six to 18 months of life, followed by a short period of developmental stagnation, then rapid regression in language and motor skills, followed by long-term stability. During the phase of rapid regression, repetitive, stereotypic hand movements replace purposeful hand use. Additional findings include fits of screaming and inconsolable crying, autistic features, panic-like attacks, bruxism, episodic apnea and/or hyperpnea, gait ataxia and apraxia, tremors, seizures, and acquired microcephaly. Males: Severe neonatal-onset encephalopathy, the most common phenotype in affected males, is characterized by a relentless clinical course that follows a metabolic-degenerative type of pattern, abnormal tone, involuntary movements, severe seizures, and breathing abnormalities. Death often occurs before age two years. [from GeneReviews]

MedGen UID:
48441
Concept ID:
C0035372
Disease or Syndrome
3.

Thanatophoric dysplasia type 1

Thanatophoric dysplasia (TD) is a short-limb skeletal dysplasia that is usually lethal in the perinatal period. TD is divided into subtypes: TD type I is characterized by micromelia with bowed femurs and, uncommonly, the presence of craniosynostosis of varying severity. TD type II is characterized by micromelia with straight femurs and uniform presence of moderate-to-severe craniosynostosis with cloverleaf skull deformity. Other features common to type I and type II include: short ribs, narrow thorax, relative macrocephaly, distinctive facial features, brachydactyly, hypotonia, and redundant skin folds along the limbs. Most affected infants die of respiratory insufficiency shortly after birth. Rare long-term survivors have been reported. [from GeneReviews]

MedGen UID:
358383
Concept ID:
C1868678
Disease or Syndrome
4.

Aicardi-Goutieres syndrome 1

Most characteristically, Aicardi-Goutières syndrome (AGS) manifests as an early-onset encephalopathy that usually, but not always, results in severe intellectual and physical disability. A subgroup of infants with AGS present at birth with abnormal neurologic findings, hepatosplenomegaly, elevated liver enzymes, and thrombocytopenia, a picture highly suggestive of congenital infection. Otherwise, most affected infants present at variable times after the first few weeks of life, frequently after a period of apparently normal development. Typically, they demonstrate the subacute onset of a severe encephalopathy characterized by extreme irritability, intermittent sterile pyrexias, loss of skills, and slowing of head growth. Over time, as many as 40% develop chilblain skin lesions on the fingers, toes, and ears. It is becoming apparent that atypical, sometimes milder, cases of AGS exist, and thus the true extent of the phenotype associated with pathogenic variants in the AGS-related genes is not yet known. [from GeneReviews]

MedGen UID:
162912
Concept ID:
C0796126
Disease or Syndrome
5.

Muscular dystrophy-dystroglycanopathy (congenital with brain and eye anomalies), type A1

Congenital muscular dystrophy-dystroglycanopathy with brain and eye anomalies (type A), which includes both the more severe Walker-Warburg syndrome (WWS) and the slightly less severe muscle-eye-brain disease (MEB), is a genetically heterogeneous autosomal recessive disorder with characteristic brain and eye malformations, profound mental retardation, congenital muscular dystrophy, and early death. The phenotype commonly includes cobblestone (type II) lissencephaly, cerebellar malformations, and retinal malformations. More variable features include macrocephaly or microcephaly, hypoplasia of midline brain structures, ventricular dilatation, microphthalmia, cleft lip/palate, and congenital contractures (Dobyns et al., 1989). Those with a more severe phenotype characterized as Walker-Warburg syndrome often die within the first year of life, whereas those characterized as having muscle-eye-brain disease may rarely acquire the ability to walk and to speak a few words. These are part of a group of disorders resulting from defective glycosylation of DAG1 (128239), collectively known as 'dystroglycanopathies' (Godfrey et al., 2007). Genetic Heterogeneity of Congenital Muscular Dystrophy-Dystroglycanopathy with Brain and Eye Anomalies (Type A) Muscular dystrophy-dystroglycanopathy with brain and eye anomalies (type A) is genetically heterogeneous and can be caused by mutation in other genes involved in DAG1 glycosylation: see MDDGA2 (613150), caused by mutation in the POMT2 gene (607439); MDDGA3 (253280), caused by mutation in the POMGNT1 gene (606822); MDDGA4 (253800), caused by mutation in the FKTN gene (607440); MDDGA5 (613153), caused by mutation in the FKRP gene (606596); MDDGA6 (613154), caused by mutation in the LARGE gene (603590); MDDGA7 (614643), caused by mutation in the ISPD gene (CRPPA; 614631); MDDGA8 (614830) caused by mutation in the GTDC2 gene (POMGNT2; 614828); MDDGA9 (616538), caused by mutation in the DAG1 gene (128239); MDDGA10 (615041), caused by mutation in the TMEM5 gene (RXYLT1; 605862); MDDGA11 (615181), caused by mutation in the B3GALNT2 gene (610194); MDDGA12 (615249), caused by mutation in the SGK196 gene (POMK; 615247); MDDGA13 (615287), caused by mutation in the B3GNT1 gene (B4GAT1; 605517); and MDDGA14 (615350), caused by mutation in the GMPPB gene (615320). [from OMIM]

MedGen UID:
924974
Concept ID:
C4284790
Disease or Syndrome
6.

Joubert syndrome 10

Classic Joubert syndrome (JS) is characterized by three primary findings: A distinctive cerebellar and brain stem malformation called the molar tooth sign (MTS). Hypotonia. Developmental delays. Often these findings are accompanied by episodic tachypnea or apnea and/or atypical eye movements. In general, the breathing abnormalities improve with age, truncal ataxia develops over time, and acquisition of gross motor milestones is delayed. Cognitive abilities are variable, ranging from severe intellectual disability to normal. Additional findings can include retinal dystrophy, renal disease, ocular colobomas, occipital encephalocele, hepatic fibrosis, polydactyly, oral hamartomas, and endocrine abnormalities. Both intra- and interfamilial variation are seen. [from GeneReviews]

MedGen UID:
440688
Concept ID:
C2749019
Disease or Syndrome
7.

Fumarase deficiency

Fumarate hydratase (FH) deficiency results in severe neonatal and early infantile encephalopathy that is characterized by poor feeding, failure to thrive, hypotonia, lethargy, and seizures. Dysmorphic facial features include frontal bossing, depressed nasal bridge, and widely spaced eyes. Many affected individuals are microcephalic. A spectrum of brain abnormalities are seen on magnetic resonance imaging, including cerebral atrophy, enlarged ventricles and generous extra-axial cerebral spinal fluid (CSF) spaces, delayed myelination for age, thinning of the corpus callosum, and an abnormally small brain stem. Brain malformations including bilateral polymicrogyria and absence of the corpus callosum can also be observed. Development is severely affected: most affected individuals are nonverbal and nonambulatory, and many die during early childhood. Less severely affected individuals with moderate cognitive impairment and long-term survival have been reported. [from GeneReviews]

MedGen UID:
87458
Concept ID:
C0342770
Disease or Syndrome
8.

Developmental and epileptic encephalopathy, 4

STXBP1 encephalopathy with epilepsy is characterized by early-onset encephalopathy with epilepsy (i.e., moderate-to-severe intellectual disability, refractory seizures, and ongoing epileptiform activity). The median age of onset of seizures is six weeks (range 1 day to 13 years). Seizure types can include infantile spasms; generalized tonic-clonic, clonic, or tonic seizures; and myoclonic, focal, atonic, and absence seizures. Epilepsy syndromes can include Ohtahara syndrome, West syndrome, Lennox-Gaustaut syndrome, and Dravet syndrome (not SCN1A-related), classic Rett syndrome (not MECP2-related), and atypical Rett syndrome (not CDKL5-related). The EEG is characterized by focal epileptic activity, burst suppression, hypsarrhythmia, or generalized spike-and-slow waves. Other findings can include abnormal tone, movement disorders (especially ataxia and dystonia), and behavior disorders (including autism spectrum disorder). Feeding difficulties are common. [from GeneReviews]

MedGen UID:
436917
Concept ID:
C2677326
Disease or Syndrome
9.

Cerebrooculofacioskeletal syndrome 1

An autosomal recessive subtype of cerebrooculofacioskeletal syndrome caused by mutation(s) in the ERCC6 gene, encoding DNA excision repair protein ERCC-6. [from NCI]

MedGen UID:
66320
Concept ID:
C0220722
Disease or Syndrome
10.

Developmental and epileptic encephalopathy, 2

Developmental and epileptic encephalopathy-2 (DEE2) is an X-linked dominant severe neurologic disorder characterized by onset of seizures in the first months of life and severe global developmental delay resulting in impaired intellectual development and poor motor control. Other features include lack of speech development, subtle dysmorphic facial features, sleep disturbances, gastrointestinal problems, and stereotypic hand movements. There is some phenotypic overlap with Rett syndrome (312750), but DEE2 is considered to be a distinct entity (summary by Fehr et al., 2013). For a discussion of genetic heterogeneity of DEE, see 308350. [from OMIM]

MedGen UID:
1663579
Concept ID:
C4750718
Disease or Syndrome
11.

Developmental and epileptic encephalopathy, 13

SCN8A-related epilepsy with encephalopathy is characterized by developmental delay, seizure onset in the first 18 months of life (mean 4 months), and intractable epilepsy characterized by multiple seizure types (generalized tonic-clonic seizures, infantile spasms, and absence and focal seizures). Epilepsy syndromes can include Lennox-Gastaut syndrome, West syndrome, and epileptic encephalopathies (e.g., Dravet syndrome). Hypotonia and movement disorders including dystonia, ataxia, and choreoathetosis are common. Psychomotor development varies from normal prior to seizure onset (with subsequent slowing or regression after seizure onset) to abnormal from birth. Intellectual disability, present in all, ranges from mild to severe (in ~50% of affected individuals). Autistic features are noted in some. Sudden unexpected death in epilepsy (SUDEP) of unknown cause has been reported in approximately 10% of published cases. To date SCN8A-related epilepsy with encephalopathy has been reported in the literature in about 50 individuals. [from GeneReviews]

MedGen UID:
482821
Concept ID:
C3281191
Disease or Syndrome
12.

Megalencephaly-polymicrogyria-polydactyly-hydrocephalus syndrome 1

MPPH (megalencephaly-postaxial polydactyly-polymicrogyria-hydrocephalus) syndrome is a developmental brain disorder characterized by megalencephaly (brain overgrowth) with the cortical malformation bilateral perisylvian polymicrogyria (BPP). At birth the occipital frontal circumference (OFC) ranges from normal to 6 standard deviations (SD) above the mean for age, sex, and gestational age; in older individuals the range is from 3 to 10 SD above the mean. A variable degree of ventriculomegaly is seen in almost all children with MPPH syndrome; nearly 50% of individuals have frank hydrocephalus. Neurologic problems associated with BPP include oromotor dysfunction (100%), epilepsy (50%), and mild-to-severe intellectual disability (100%). Postaxial hexadactyly occurs in 50% of individuals with MPPH syndrome. [from GeneReviews]

MedGen UID:
861164
Concept ID:
C4012727
Disease or Syndrome
13.

Muscular dystrophy-dystroglycanopathy (congenital with brain and eye anomalies), type A5

Congenital muscular dystrophy-dystroglycanopathy with brain and eye anomalies (type A), which includes both the more severe Walker-Warburg syndrome (WWS) and the slightly less severe muscle-eye-brain disease (MEB), is an autosomal recessive disorder with characteristic brain and eye malformations, profound mental retardation, congenital muscular dystrophy, and death usually in the first years of life. It represents the most severe end of a phenotypic spectrum of similar disorders resulting from defective glycosylation of DAG1 (128239), collectively known as 'dystroglycanopathies' (Beltran-Valero de Bernabe et al., 2004). For a general phenotypic description and a discussion of genetic heterogeneity of muscular dystrophy-dystroglycanopathy type A, see MDDGA1 (236670). [from OMIM]

MedGen UID:
461763
Concept ID:
C3150413
Disease or Syndrome
14.

Warburg micro syndrome 3

RAB18 deficiency is the molecular deficit underlying both Warburg micro syndrome (characterized by eye, nervous system, and endocrine abnormalities) and Martsolf syndrome (characterized by similar – but milder – findings). To date Warburg micro syndrome comprises >96% of reported individuals with genetically defined RAB18 deficiency. The hallmark ophthalmologic findings are bilateral congenital cataracts, usually accompanied by microphthalmia, microcornea (diameter <10), and small atonic pupils. Poor vision despite early cataract surgery likely results from progressive optic atrophy and cortical visual impairment. Individuals with Warburg micro syndrome have severe to profound intellectual disability (ID); those with Martsolf syndrome have mild to moderate ID. Some individuals with RAB18 deficiency also have epilepsy. In Warburg micro syndrome, a progressive ascending spastic paraplegia typically begins with spastic diplegia and contractures during the first year, followed by upper-limb involvement leading to spastic quadriplegia after about age five years, often eventually causing breathing difficulties. In Martsolf syndrome infantile hypotonia is followed primarily by slowly progressive lower-limb spasticity. Hypogonadism – when present – manifests in both syndromes, in males as micropenis and/or cryptorchidism and in females as hypoplastic labia minora, clitoral hypoplasia, and small introitus. [from GeneReviews]

MedGen UID:
481833
Concept ID:
C3280203
Disease or Syndrome
15.

Matthew-Wood syndrome

Syndromic microphthalmia-9 (MCOPS9), also referred to as pulmonary hypoplasia-diaphragmatic hernia-anophthalmia-cardiac defect, is characterized by bilateral clinical anophthalmia, pulmonary hypoplasia/aplasia, cardiac malformations, and diaphragmatic defects. The phenotype is variable, ranging from isolated clinical anophthalmia or microphthalmia to complex presentations involving the cardiac, pulmonary, diaphragmatic, and renal systems. At its most severe, infants are born without pulmonary structures and die soon after birth (Marcadier et al., 2015). [from OMIM]

MedGen UID:
318679
Concept ID:
C1832661
Disease or Syndrome
16.

Muscular dystrophy-dystroglycanopathy (congenital with brain and eye anomalies), type A2

Congenital muscular dystrophy-dystroglycanopathy with brain and eye anomalies (type A), which includes both the more severe Walker-Warburg syndrome (WWS) and the slightly less severe muscle-eye-brain disease (MEB), is an autosomal recessive disorder with characteristic brain and eye malformations, profound mental retardation, congenital muscular dystrophy, and death usually in the first years of life. It represents the most severe end of a phenotypic spectrum of similar disorders resulting from defective glycosylation of DAG1 (128239), collectively known as 'dystroglycanopathies' (van Reeuwijk et al., 2005). For a general phenotypic description and a discussion of genetic heterogeneity of muscular dystrophy-dystroglycanopathy type A, see MDDGA1 (236670). [from OMIM]

MedGen UID:
461761
Concept ID:
C3150411
Disease or Syndrome
17.

Muscular dystrophy-dystroglycanopathy (congenital with brain and eye anomalies), type A, 7

Congenital muscular dystrophy-dystroglycanopathy with brain and eye anomalies (type A), which includes both the more severe Walker-Warburg syndrome (WWS) and the slightly less severe muscle-eye-brain disease (MEB), is an autosomal recessive disorder with characteristic brain and eye malformations, profound mental retardation, congenital muscular dystrophy, and death usually in the first years of life. It represents the most severe end of a phenotypic spectrum of similar disorders resulting from defective glycosylation of alpha-dystroglycan (DAG1; 128239), collectively known as 'dystroglycanopathies' (summary by Roscioli et al., 2012). For a general phenotypic description and a discussion of genetic heterogeneity of muscular dystrophy-dystroglycanopathy type A, see MDDGA1 (236670). [from OMIM]

MedGen UID:
766244
Concept ID:
C3553330
Disease or Syndrome
18.

Developmental and epileptic encephalopathy, 5

Developmental and epileptic encephalopathy-5 (DEE5) is a neurologic disorder characterized by global developmental delay and the onset of tonic seizures or infantile spasms in the first months of life. The seizures tend to be refractory to treatment, and EEG shows hypsarrhythmia, consistent with a clinical diagnosis of West syndrome. Affected individuals have severely impaired psychomotor development with lack of visual attention, poor head control, feeding difficulties, microcephaly, and spastic quadriplegia. Brain imaging may show cerebral atrophy and hypomyelination (summary by Saitsu et al., 2010). For a general phenotypic description and a discussion of genetic heterogeneity of developmental and epileptic encephalopathy, see 308350. [from OMIM]

MedGen UID:
462081
Concept ID:
C3150731
Disease or Syndrome
19.

Muscular dystrophy-dystroglycanopathy type B6

MDDGB6 is an autosomal recessive congenital muscular dystrophy with impaired intellectual development and structural brain abnormalities (Longman et al., 2003). It is part of a group of similar disorders resulting from defective glycosylation of alpha-dystroglycan (DAG1; 128239), collectively known as 'dystroglycanopathies' (Mercuri et al., 2009). For a discussion of genetic heterogeneity of congenital muscular dystrophy-dystroglycanopathy type B, see MDDGB1 (613155). [from OMIM]

MedGen UID:
373284
Concept ID:
C1837229
Disease or Syndrome
20.

Mosaic variegated aneuploidy syndrome 1

Mosaic variegated aneuploidy (MVA) syndrome is a rare disorder in which some cells in the body have an abnormal number of chromosomes instead of the usual 46 chromosomes, a situation known as aneuploidy. Most commonly, cells have an extra chromosome, which is called trisomy, or are missing a chromosome, which is known as monosomy. In MVA syndrome, some cells are aneuploid and others have the normal number of chromosomes, which is a phenomenon known as mosaicism. Typically, at least one-quarter of cells in affected individuals have an abnormal number of chromosomes. Because the additional or missing chromosomes vary among the abnormal cells, the aneuploidy is described as variegated.

There are at least three types of MVA syndrome, each with a different genetic cause. Type 1 is the most common and displays the classic signs and symptoms described above. Type 2 appears to have slightly different signs and symptoms than type 1, although the small number of affected individuals makes it difficult to define its characteristic features. Individuals with MVA syndrome type 2 grow slowly before and after birth; however, their head size is typically normal. Some people with MVA syndrome type 2 have unusually short arms. Individuals with MVA syndrome type 2 do not seem to have an increased risk of cancer. Another form of MVA syndrome is characterized by a high risk of developing Wilms tumor. Individuals with this form may also have other signs and symptoms typical of MVA syndrome type 1.

In MVA syndrome, growth before birth is slow (intrauterine growth restriction). After birth, affected individuals continue to grow at a slow rate and are shorter than average. In addition, they typically have an unusually small head size (microcephaly). Another common feature of MVA syndrome is an increased risk of developing cancer in childhood. Cancers that occur most frequently in affected individuals include a cancer of muscle tissue called rhabdomyosarcoma, a form of kidney cancer known as Wilms tumor, and a cancer of the blood-forming tissue known as leukemia.

Less commonly, people with MVA syndrome have eye abnormalities or distinctive facial features, such as a broad nasal bridge and low-set ears. Some affected individuals have brain abnormalities, the most common of which is called Dandy-Walker malformation. Intellectual disability, seizures, and other health problems can also occur in people with MVA syndrome. [from MedlinePlus Genetics]

MedGen UID:
338026
Concept ID:
C1850343
Disease or Syndrome
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