Autism: an overview of genetic aetiology.

Autism is a pervasive developmental disorder characterised by impairment in social interaction and in communication, with unusual behaviour. Genetic factors are predominant in autism pathogenesis. Interactions between multiple genes cause "idiopathic" autism but epigenetic factors and exposure to environmental modifiers may contribute to variable expression of autism-related traits. The genetic polymorphism and the phenotypic heterogeneity make the autism a complex disorder to study. Genetic research on families with multiple affected children and biochemical mechanisms studies represent the sources for identifying the susceptibility genes in autism. Children with dysmorphic features, congenital anomalies, mental retardation, or family members with developmental disorders are those most likely to benefit from extensive medical testing and genetic consultation.