Candidate susceptibility genes for Autism

Autism is a pervasive developmental disorder that affects approximately one child in every 2,000 with a male:female ratio of 4:1 (Fombonne, 1999). The primary characteristics of autism were first described by Leo Kanner (1943) as an inability to relate to people and situations in an ordinary way, stereotyped movement, normal cognitive potential, and excellent rote memory. Currently, autism is recognized as a complex neurodevelopmental disorder characterized by the inability to establish and maintain relationships with others and impairment in nonverbal and verbal communications, accompanied by delay or lack of language, stereotyped behavior, repetitive movements, and restricted interests (Bailey et al., 1996). Autism is often accompanied by epilepsy and mental retardation. The onset of the disorder is within the first 3 years of life, and diagnosis is based mainly on the observation of behavioral dysfunctions and abnormal development of language. The spectrum of clinical manifestations and the severity of the disorder are variable, and they differ significantly even among siblings (Bailey et al., 1996; Happe and Frith 1996; Maestrini et al., 2000). Occasionally, autism overlaps with fragile X syndrome (August and Lockhart, 1984; Feinstein and Reiss, 1998), tuberous sclerosis (Smalley et al., 1992), or Angelman syndrome (Williams et al., 2001), further complicating diagnosis.