Autism, Susceptibility To, 13

Description

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).

For a discussion of genetic heterogeneity of autism, see 209850.

Mapping

By genomewide linkage analysis of 26 families with autism, comprising 65 affected individuals, Ma et al. (2007) found significant linkage to chromosome 12q14.2 (multipoint parametric lod score of 3.02 at SNP rs1445442 under a recessive model). Linkage to this region was enhanced significantly (lod score of 4.51) in families with only males affected, suggesting a gender-specific effect. Haplotype analysis localized the potential autism locus to a 4-cM region shared among the affected individuals across linked families.