Asperger syndrome is considered to be a form of childhood autism (see, e.g., 209850). The DSM-IV (American Psychiatric Association, 1994) specifies several diagnostic criteria for Asperger syndrome, which has many of the same features as autism. In general, patients with Asperger syndrome and autism exhibit qualitative impairment in social interaction, as manifest by impairment in the use of nonverbal behaviors such as eye-to-eye gaze, facial expression, body postures, and gestures, failure to develop appropriate peer relationships, and lack of social sharing or reciprocity. Patients also exhibit restricted, repetitive and stereotyped patterns of behavior, interests, and activities, including abnormal preoccupation with certain activities and inflexible adherence to routines or rituals. Asperger syndrome is primarily distinguished from autism by the higher cognitive abilities and a more normal and timely development of language and communicative phrases. Gillberg et al. (2001) described the development of the Asperger syndrome (and high-functioning autism) Diagnostic Interview (ASDI), which they claimed has a strong validity in the diagnosis of the disorder. Genetic Heterogeneity of Susceptibility to Asperger Syndrome ASPG1 maps to chromosome 3q. Other autosomal loci include ASPG2 (608631) on chromosome 17p, ASPG3 (608781) on 1q21-q22, and ASPG4 (609954) on 3p24-p21.