Global developmental delay, and Schizophrenia

Deletions at 2p16.3 involving exons of NRXN1 are associated with susceptibility to autism, schizophrenia (SCZD17), developmental delay, intellectual disability, and dysmorphic features. The phenotype is highly variable and shows incomplete penetrance (summary by Dabell et al., 2013).For a phenotypic description and a discussion of genetic heterogeneity of schizophrenia, see {181500}.

• Intellectual disability
• Seizures
• Global developmental delay
• Delayed speech and language development
• Abnormality of the skeletal system

SOURCES: OMIM MENDELIAN

Hyperprolinaemia type I is an inborn error of proline metabolism characterised by elevated levels of proline in the plasma and urine. The prevalence is unknown. The disorder is generally considered to be benign but associations with renal abnormalities, epileptic seizures, and other neurological manifestations, as well as certain forms of schizophrenia have been reported. It is transmitted as an autosomal recessive trait and is caused by mutations in the proline dehydrogenase or proline oxidase gene (PRODH or POX, 22q11.2).

HYPERPROLINEMIA TYPE 1 Is also known as hpi|proline oxidase deficiency

• Intellectual disability
• Seizures
• Global developmental delay
• Generalized hypotonia
• Hearing impairment

SOURCES: OMIM ORPHANET MENDELIAN

Spinocerebellar ataxia-7 (SCA7) is an autosomal dominant neurodegenerative disorder characterized by adult onset of progressive cerebellar ataxia associated with pigmental macular dystrophy. In her classification of ataxia, Harding (1982) referred to progressive cerebellar ataxia with pigmentary macular degeneration as type II ADCA (autosomal dominant cerebellar ataxia). The age at onset, degree of severity, and rate of progression vary among and within families. Associated neurologic signs, such as ophthalmoplegia, pyramidal or extrapyramidal signs, deep sensory loss, or dementia, are also variable. Genetic anticipation is observed and is greater in paternal than in maternal transmissions (Benomar et al., 1994; summary by David et al., 1996).For a general discussion of autosomal dominant spinocerebellar ataxia, see SCA1 (OMIM ).

SPINOCEREBELLAR ATAXIA 7; SCA7 Is also known as opca iii|opca with macular degeneration and external ophthalmoplegia|adca, type ii|olivopontocerebellar atrophy iii|opca3|opca with retinal degeneration|autosomal dominant cerebellar ataxia, type ii

• Global developmental delay
• Generalized hypotonia
• Ataxia
• Nystagmus
• Failure to thrive

SOURCES: OMIM MENDELIAN

Congenital adrenal hypoplasia (AHC) is a rare disorder that can be inherited in an X-linked or autosomal recessive (see {240200}) pattern. In X-linked AHC, primary adrenocortical failure occurs because the adrenal glands lack the permanent adult cortical zone. The remaining cells are termed 'cytomegalic' because they are larger than typical fetal adrenal cells (Hay et al., 1981; Reutens et al., 1999).Patients with AHC usually present in early infancy with primary adrenal failure. Hypogonadotropic hypogonadism (HHG) is a hallmark of the disorder, and is recognized during adolescence because of the absence or interruption of normal pubertal development. Abnormal spermatogenesis has also been observed in these patients. Milder forms of the disease have been described, with adrenal insufficiency sometimes occurring in childhood or even early adulthood. A few cases of partial HHG have been reported (summary by Raffin-Sanson et al., 2013). Transient precocious sexual development in infancy or early childhood can be a prominent feature of AHC (Landau et al., 2010).A contiguous gene syndrome involving a combination of congenital adrenal hypoplasia, glycerol kinase deficiency (OMIM ), and Duchenne muscular dystrophy (DMD ) is caused by deletion of multiple genes on chromosome Xp21 (see {300679}).

CYTOMEGALIC CONGENITAL ADRENAL HYPOPLASIA Is also known as ahch|cytomegalic adrenocortical hypoplasia|x-linked congenital adrenal hypoplasia|adrenal hypoplasia, congenital, with hypogonadotropic hypogonadism|ahc with isolated gonadotropin deficiency|addison disease, x-linked|ahx|ahc with hhg

• Global developmental delay
• Hearing impairment
• Failure to thrive
• Cryptorchidism
• Vomiting

SOURCES: OMIM ORPHANET MENDELIAN

Usher syndrome type I is an autosomal recessive condition characterized by profound congenital hearing impairment with unintelligible speech, early retinitis pigmentosa (usually evident within the first decade), and constant vestibular dysfunction. Type I is distinguished from type II (OMIM ) on the basis of severity of hearing loss and the extent of vestibular involvement. Type I patients are profoundly deaf, whereas type II patients are 'hard of hearing.' Vestibular function is defective in type I patients, whereas type II patients have normal vestibular function (Moller et al., 1989). Patients with type III (USH3 ) have progressive hearing loss. Genetic Heterogeneity of Usher Syndrome Type IUSH type I is genetically heterogeneous. USH1C (OMIM ), the 'Acadian variety,' is caused by mutation in harmonin (OMIM ), on 11p15. USH1D (OMIM ) is caused by mutation in the cadherin-23 (CDH23 ) on 10q21. USH1F (OMIM ) is caused by mutation in the protocadherin-15 (PCDH15 ) on 10q22. USH1G (OMIM ) is caused by mutation in the SANS gene (OMIM ), on 17q25. USH1E (OMIM ) maps to 21q21, and USH1H (OMIM ) maps to 15q22-q23. USH1J (OMIM ) is caused by mutation in the CIB2 gene (OMIM ) on 15q24. USH1K (OMIM ) maps to chromosome 10p11.21-q21.1.A form of USH type I in which affected members carried heterozygous mutations in both CDH23 and PCDH15 has been reported (USH1D/F; see {601067}), thus supporting a digenic model for some individuals with this phenotype.Gerber et al. (2006) presented evidence that the form of USH1 previously called USH1A, or the 'French variety,' and mapped to chromosome 14 does not in fact exist; mutations in the MYO7A gene were found in most of these families, and in others the phenotype was found to map to other loci.Ahmed et al. (2003) reviewed the molecular genetics of Usher syndrome and indicated that at least 12 loci had been identified as underlying the 3 different clinical subtypes.

USHER SYNDROME TYPE 1 Is also known as ush1|retinitis pigmentosa and congenital deafness|us1

• Intellectual disability
• Global developmental delay
• Hearing impairment
• Ataxia
• Sensorineural hearing impairment

SOURCES: OMIM ORPHANET MENDELIAN

Xq25 duplication syndrome is an X-linked neurodevelopmental disorder characterized by delayed development and intellectual disability associated with abnormal behavior and dysmorphic facial features. Additional variable features may include thin corpus callosum on brain imaging and sleep disturbances. Carrier females may be mildly affected (summary by Leroy et al., 2016).

XQ25 MICRODUPLICATION SYNDROME Is also known as xq25 microtriplication|dup(x)(q25)

• Intellectual disability
• Seizures
• Global developmental delay
• Short stature
• Generalized hypotonia

SOURCES: ORPHANET OMIM MENDELIAN

1q21.1 microduplication syndrome is a rare partial autosomal trisomy/tetrasomy with incomplete penetrance and variable expression characterized by macrocephaly, developmental delay, intellectual disability, psychiatric disturbances (autism spectrum disorder, attention deficit hyperactivity disorder, schizophrenia, mood disorders) and mild facial dysmorphism (high forehead, hypertelorism). Other associated features include congenital heart defects, hypotonia, short stature, scoliosis.

1Q21.1 MICRODUPLICATION SYNDROME Is also known as trisomy 1q21.1|dup(1)(q21.1)

• Intellectual disability
• Seizures
• Global developmental delay
• Short stature
• Generalized hypotonia

SOURCES: ORPHANET OMIM MESH MENDELIAN

Bilateral striopallidodentate calcinosis (BSPDC, also erroneously called Fahr disease) is characterized by the accumulation of calcium deposits in different brain regions, particularly the basal ganglia and dentate nucleus, and is often associated with neurodegeneration.

BILATERAL STRIOPALLIDODENTATE CALCINOSIS Is also known as cerebrovascular ferrocalcinosis|primary familial brain calcification|ferrocalcinosis, cerebrovascular|pfbc|bspdc|striopallidodentate calcinosis, bilateral|cerebral calcification, nonarteriosclerotic, idiopathic, adult-onset|basal ganglia calcification, id

• Intellectual disability
• Seizures
• Global developmental delay
• Microcephaly
• Ataxia

SOURCES: ORPHANET OMIM MENDELIAN

Niemann-Pick type C (NPC) disease is an autosomal recessive lipid storage disorder characterized by progressive neurodegeneration. Approximately 95% of cases are caused by mutations in the NPC1 gene, referred to as type C1; 5% are caused by mutations in the NPC2 gene (OMIM ), referred to as type C2 (OMIM ). The clinical manifestations of types C1 and C2 are similar because the respective genes are both involved in egress of lipids, particularly cholesterol, from late endosomes or lysosomes (summary by Vance, 2006).Historically, Crocker (1961) delineated 4 types of Niemann-Pick disease: the classic infantile form (type A; {257200}), the visceral form (type B; {607616}), the subacute or juvenile form (type C), and the Nova Scotian variant (type D). Types C1 and D are indistinguishable except for the occurrence of type D in patients of Nova Scotian Acadian ancestry. Since then, types E and F have also been described (see {607616}), and phenotypic variation within each group has also been described.

NIEMANN-PICK DISEASE, TYPE C1; NPC1 Is also known as niemann-pick disease, type c|niemann-pick disease with cholesterol esterification block|neurovisceral storage disease with vertical supranuclear ophthalmoplegia|niemann-pick disease, subacute juvenile form|npc|niemann-pick disease without sphingomyelinase

• Intellectual disability
• Seizures
• Global developmental delay
• Generalized hypotonia
• Ataxia

SOURCES: ORPHANET OMIM MENDELIAN

15q13.3 microdeletion (microdel15q13.3) syndrome is characterized by a wide spectrum of neurodevelopmental disorders with no or subtle dysmorphic features.

15Q13.3 MICRODELETION SYNDROME Is also known as del(15)(q13.3)|chromosome 15q13.3 microdeletion syndrome|monosomy 15q13.3

• Seizures
• Schizophrenia
• Bipolar affective disorder

SOURCES: MESH MENDELIAN