MedGen

Charcot-Marie-Tooth disease is a sensorineural peripheral polyneuropathy. Affecting approximately 1 in 2,500 individuals, Charcot-Marie-Tooth disease is the most common inherited disorder of the peripheral nervous system (Skre, 1974). Autosomal dominant, autosomal recessive, and X-linked forms have been recognized. Classification On the basis of electrophysiologic properties and histopathology, CMT has been divided into primary peripheral demyelinating (type 1, or HMSNI) and primary peripheral axonal (type 2, or HMSNII) neuropathies. The demyelinating neuropathies classified as CMT type 1 are characterized by severely reduced motor NCVs (less than 38 m/s) and segmental demyelination and remyelination with onion bulb formations on nerve biopsy. The axonal neuropathies classified as CMT type 2 are characterized by normal or mildly reduced NCVs and chronic axonal degeneration and regeneration on nerve biopsy (see CMT2A1; 118210). Distal hereditary motor neuropathy (dHMN) (see 158590), or spinal CMT, is characterized by exclusive motor involvement and sparing of sensory nerves (Pareyson, 1999). McAlpine (1989) proposed that the forms of CMT with very slow nerve conduction be given the gene symbol CMT1A (118220) and CMT1B, CMT1A being the gene on chromosome 17 and CMT1B being the gene on chromosome 1. CMT2 was the proposed symbol for the autosomal locus responsible for the moderately slow nerve conduction form of the disease (axonal). For a phenotypic description and discussion of genetic heterogeneity of the various subtypes of CMT, see CMTX1 (302800), CMT2A1 (118210), CMT3 (DSS; 145900), CMT4A (214400), and CMTDIB (606482). Genetic Heterogeneity of Autosomal Dominant Demyelinating CMT1 Autosomal dominant demyelinating CMT1 is a genetically heterogeneous disorder and can be caused by mutations in different genes; see CMT1A (118220), CMT1C (601098), CMT1D (607678), CMT1E (607734), CMT1F (607734), CMT1G (618279), CMT1H (619764), CMT1I (619742), and CMT1J (620111). See also 608236 for a related phenotype characterized by isolated slowed nerve conduction velocities (NCVs). [from OMIM]

The nephrotic syndrome is characterized clinically by proteinuria, hypoalbuminemia, hyperlipidemia, and edema. Kidney biopsies show nonspecific histologic changes such as minimal change, focal segmental glomerulosclerosis (FSGS), and diffuse mesangial proliferation. Approximately 20% of affected individuals have an inherited steroid-resistant form and progress to end-stage renal failure (summary by Fuchshuber et al., 1996). Nephrotic syndrome type 1 (NPHS1) is characterized by prenatal onset of massive proteinuria followed by severe steroid-resistant nephrotic syndrome apparent at birth with rapid progression to end-stage renal failure (Kestila et al., 1998). Because of confusion in the literature regarding use of the terms 'nephrotic syndrome' and 'focal segmental glomerulosclerosis' (see NOMENCLATURE section), these disorders in OMIM are classified as NPHS or FSGS according to how they were first designated in the literature. Genetic Heterogeneity of Nephrotic Syndrome and Focal Segmental Glomerulosclerosis Nephrotic syndrome and FSGS are genetically heterogeneous disorders representing a spectrum of hereditary renal diseases. See also NPHS2 (600995), caused by mutation in the podocin gene (604766); NPHS3 (610725), caused by mutation in the PLCE1 gene (608414); NPHS4 (256370), caused by mutation in the WT1 gene (607102); NPHS5 (614199), caused by mutation in the LAMB2 gene (150325); NPHS6 (614196), caused by mutation in the PTPRO gene (600579); NPHS7 (615008), caused by mutation in the DGKE gene (601440); NPHS8 (615244), caused by mutation in the ARHGDIA gene (601925); NPHS9 (615573), caused by mutation in the COQ8B gene (615567); NPHS10 (615861), caused by mutation in the EMP2 gene (602334); NPHS11 (616730), caused by mutation in the NUP107 gene (607617); NPHS12 (616892), caused by mutation in the NUP93 gene (614351); NPHS13 (616893), caused by mutation in the NUP205 gene (614352); NPHS14 (617575), caused by mutation in the SGPL1 gene (603729); NPHS15 (617609), caused by mutation in the MAGI2 gene (606382); NPHS16 (617783), caused by mutation in the KANK2 gene (614610), NPHS17 (618176), caused by mutation in the NUP85 gene (170285); NPHS18 (618177), caused by mutation in the NUP133 gene (607613); NPHS19 (618178), caused by mutation in the NUP160 gene (607614); NPHS20 (301028), caused by mutation in the TBC1D8B gene (301027); NPHS21 (618594) caused by mutation in the AVIL gene (613397); NPHS22 (619155), caused by mutation in the NOS1AP gene (605551); NPHS23 (619201), caused by mutation in the KIRREL1 gene (607428); NPHS24 (619263), caused by mutation in the DAAM2 gene (606627); and NPHS26 (620049), caused by mutation in the LAMA5 gene (601033). The symbol NPHS25 has been used as an alternative designation for NPHS21. See also FSGS1 (603278), caused by mutation in the ACTN4 gene (604638); FSGS2 (603965), caused by mutation in the TRPC6 gene (603652); FSGS3 (607832), associated with variation in the CD2AP gene (604241); FSGS4 (612551), mapped to chromosome 22q12; FSGS5 (613237), caused by mutation in the INF2 gene (610982); FSGS6 (614131), caused by mutation in the MYO1E gene (601479); FSGS7 (616002), caused by mutation in the PAX2 gene (167409); FSGS8 (616032), caused by mutation in the ANLN gene (616027); and FSGS9 (616220), caused by mutation in the CRB2 gene (609720). [from OMIM]

Autism, the prototypic pervasive developmental disorder (PDD), is usually apparent by 3 years of age. It is characterized by a triad of limited or absent verbal communication, a lack of reciprocal social interaction or responsiveness, and restricted, stereotypic, and ritualized patterns of interests and behavior (Bailey et al., 1996; Risch et al., 1999). 'Autism spectrum disorder,' sometimes referred to as ASD, is a broader phenotype encompassing the less severe disorders Asperger syndrome (see ASPG1; 608638) and pervasive developmental disorder, not otherwise specified (PDD-NOS). 'Broad autism phenotype' includes individuals with some symptoms of autism, but who do not meet the full criteria for autism or other disorders. Mental retardation coexists in approximately two-thirds of individuals with ASD, except for Asperger syndrome, in which mental retardation is conspicuously absent (Jones et al., 2008). Genetic studies in autism often include family members with these less stringent diagnoses (Schellenberg et al., 2006). Levy et al. (2009) provided a general review of autism and autism spectrum disorder, including epidemiology, characteristics of the disorder, diagnosis, neurobiologic hypotheses for the etiology, genetics, and treatment options. Genetic Heterogeneity of Autism Autism is considered to be a complex multifactorial disorder involving many genes. Accordingly, several loci have been identified, some or all of which may contribute to the phenotype. Included in this entry is AUTS1, which has been mapped to chromosome 7q22. Other susceptibility loci include AUTS3 (608049), which maps to chromosome 13q14; AUTS4 (608636), which maps to chromosome 15q11; AUTS6 (609378), which maps to chromosome 17q11; AUTS7 (610676), which maps to chromosome 17q21; AUTS8 (607373), which maps to chromosome 3q25-q27; AUTS9 (611015), which maps to chromosome 7q31; AUTS10 (611016), which maps to chromosome 7q36; AUTS11 (610836), which maps to chromosome 1q41; AUTS12 (610838), which maps to chromosome 21p13-q11; AUTS13 (610908), which maps to chromosome 12q14; AUTS14A (611913), which has been found in patients with a deletion of a region of 16p11.2; AUTS14B (614671), which has been found in patients with a duplication of a region of 16p11.2; AUTS15 (612100), associated with mutation in the CNTNAP2 gene (604569) on chromosome 7q35-q36; AUTS16 (613410), associated with mutation in the SLC9A9 gene (608396) on chromosome 3q24; AUTS17 (613436), associated with mutation in the SHANK2 gene (603290) on chromosome 11q13; AUTS18 (615032), associated with mutation in the CHD8 gene (610528) on chromosome 14q11; AUTS19 (615091), associated with mutation in the EIF4E gene (133440) on chromosome 4q23; and AUTS20 (618830), associated with mutation in the NLGN1 gene (600568) on chromosome 3q26. (NOTE: the symbol 'AUTS2' has been used to refer to a gene on chromosome 7q11 (KIAA0442; 607270) and therefore is not used as a part of this autism locus series.) There are several X-linked forms of autism susceptibility: AUTSX1 (300425), associated with mutations in the NLGN3 gene (300336); AUTSX2 (300495), associated with mutations in NLGN4 (300427); AUTSX3 (300496), associated with mutations in MECP2 (300005); AUTSX4 (300830), associated with variation in the region on chromosome Xp22.11 containing the PTCHD1 gene (300828); AUTSX5 (300847), associated with mutations in the RPL10 gene (312173); and AUTSX6 (300872), associated with mutation in the TMLHE gene (300777). A locus on chromosome 2q (606053) associated with a phenotype including intellectual disability and speech deficits was formerly designated AUTS5. Folstein and Rosen-Sheidley (2001) reviewed the genetics of autism. [from OMIM]

Zellweger syndrome is an autosomal recessive systemic disorder characterized clinically by severe neurologic dysfunction, craniofacial abnormalities, and liver dysfunction, and biochemically by the absence of peroxisomes. Most severely affected individuals with classic Zellweger syndrome phenotype die within the first year of life (summary by Wanders, 2004). 'Zellweger syndrome' is the prototype of a large group of peroxisomal disorders, which can be classified into 2 main groups: (1) disorders of peroxisome biogenesis and (2) single peroxisomal enzyme deficiencies (see 264470). The peroxisome biogenesis disorders (PBDs) fall into 4 main phenotypic classes. Three of them, Zellweger syndrome, neonatal adrenoleukodystrophy (NALD), and infantile Refsum disease (IRD), have multiple complementation groups and form a spectrum of overlapping features, with the most severe being the Zellweger syndrome and the least severe infantile Refsum disease. The fourth group, rhizomelic chondrodysplasia punctata (RCDP1; 215100), is a distinct PBD phenotype (summary by Moser et al., 1995, Wanders, 2004). Heimler syndrome, a rare autosomal recessive disorder encompassing sensorineural hearing loss, enamel hypoplasia of the secondary dentition, and nail abnormalities, represents a discrete phenotypic entity at the mildest end of the PBD spectrum (Ratbi et al., 2015). Genetic Heterogeneity of Zellweger Syndrome Zellweger syndrome (denoted by the suffix 'A' in the symbol) is a genetically heterogeneous disorder and can be caused by mutation in any one of several genes, known as pexins, involved in peroxisome biogenesis. The pexin (PEX) genes encode proteins essential for the assembly of functional peroxisomes (summary by Distel et al., 1996). Forms of Zellweger syndrome include PBD1A, caused by mutation in the PEX1 gene on chromosome 7q21; PBD2A (214110), caused by mutation in the PEX5 (600414) gene on chromosome 12p13; PBD3A (614859), caused by mutation in the PEX12 (601758) gene on chromosome 17; PBD4A (614862), caused by mutation in the PEX6 (601498) gene on chromosome 6p21; PBD5A (614866), caused by mutation in the PEX2 (170993) gene on chromosome 8q21; PBD6A (614870), caused by mutation in the PEX10 (602859) gene on chromosome 1p36; PBD7A (614872), caused by mutation in the PEX26 (608666) gene on chromosome 22q11; PBD8A (614876), caused by mutation in the PEX16 (603360) gene on chromosome 11p12; PBD10A (614882), caused by mutation in the PEX3 (603164) gene on chromosome 6q23-q24; PBD11A (614883), caused by mutation in the PEX13 (601789) gene on chromosome 2p15; PBD12A (614886), caused by mutation in the PEX19 (600279) gene on chromosome 1q22; and PBD13A (614887), caused by mutation in the PEX14 gene (601791) on chromosome 1p36.2. Mutation in the pexin genes also causes the less severe phenotypes of neonatal adrenoleukodystrophy (NALD) and infantile Refsum disease (IRD); see PBD1B (601539) for a phenotypic description and discussion of genetic heterogeneity of these PBDs. Heimler syndrome-1 (HMLR1; 234580) and -2 (HMLR2; 616617) are caused by mutation in the PEX1 and PEX6 genes, respectively. The rhizomelic chondrodysplasia subtype of PBD (RCDP1, PBD9; 215100), and a PBD without rhizomelia (PBD9B; 614879), are caused by mutation in the PEX7 gene (601757) on chromosome 6q22-q24. In addition to the defects in peroxisome assembly, Distel et al. (1996) noted that peroxisomal disorders include a number of single peroxisomal enzyme deficiencies: X-linked adrenoleukodystrophy (ALD; 300100), acyl-coenzyme A oxidase deficiency (264470), DHAPAT deficiency (222765), alkyl-DHAP synthase deficiency (600121), glutaric aciduria type III (231690), classic Refsum disease (266500), hyperoxaluria type I (259900), and acatalasia (115500). A peroxisomal and mitochondrial fission defect results in a lethal encephalopathy (EMPF; 614388). [from OMIM]

Mutations in the CRYAA gene have been found to cause multiple types of cataract, which have been described as nuclear, zonular central nuclear, laminar, lamellar, anterior polar, posterior polar, cortical, embryonal, anterior subcapsular, fan-shaped, and total. Cataract associated with microcornea, sometimes called the cataract-microcornea syndrome, is also caused by mutation in the CRYAA gene. Both autosomal dominant and autosomal recessive modes of inheritance have been reported. The symbol CATC1 was formerly used for the autosomal recessive form of cataract caused by mutation in the CRYAA gene. [from OMIM]

Mutations in the CRYBB2 gene have been found to cause several types of cataract, which have been described as congenital cerulean, 'blue dot,' Coppock-like, sutural with punctate and cerulean opacities, pulverulent embryonal, pulverulent with cortical opacities, dense posterior star-shaped subcapsular with pulverulent opacities in the cortical and embryonal regions, and dense embryonal. Before it was known that mutations in the CRYBB2 gene cause several types of cataract, the preferred title of this entry was 'Cataract, Congenital, Cerulean Type 2,' with the symbol CCA2. [from OMIM]

Mutations in the CRYGC gene have been found to cause several types of cataract, which have been described as Coppock-like; embryonic, fetal, infantile nuclear; zonular pulverulent; and lamellar. Some patients also exhibit microcornea. Before it was known that mutations in the CRYGC gene cause several types of cataract, this entry was titled 'Cataract, Coppock-like,' with the symbol CCL. [from OMIM]