Genetics of childhood disorders: XLII. Autism, part 1: Diagnosis and assessment in autistic spectrum disorders.

Autism is a developmental disorder that is evident in infancy or early childhood and results in a broad range of behaviors and, often, lifelong impairments. Now conceptualized as a spectrum of related diagnostic categories, autistic spectrum disorders (ASD) involve severe difficulties in basic aspects of social behavior and communication, such as eye contact, facial expressions, and the development of spontaneous, reciprocal language, which, for reasons not well understood, are associated with behaviors characterized by repetition and restriction, ranging from finger-flicking to compulsive touching to complex preoccupations with electrical appliances or highly circumscribed interests such as names of radio stations or Scottish clans. Such patterns, which often change with development, occur in individuals who function intellectually from profound mental retardation to the superior range of intelligence. Regardless of the level of functioning, all these cases share basic disturbances in social interaction and communication. Manifestations of the severity of the disorder also range from severe to relatively mild. The spectrum includes classical cases of autism, as defined by the presence of severe deficits in the three relevant domains, to cases that include significant social impairment, but without communication disorder or without repetitive behaviors. There are also differences in developmental trajectories, both between ASD and within them. Thus childhood disintegrative disorder is defined by normal development until at least age 2 years, followed by loss of skills across multiple areas of functioning. Asperger’s disorder is defined by severe social deficits and restricted interests or behaviors that are not accompanied by language delay or mental retardation. Asperger’s disorder is typically diagnosed later; it is not clear if behavior patterns actually develop later, or if there is later recognition of the abnormality of these behaviors as they begin to cause impairment in social situations. The assumption, as discussed in more detail below, is that ASD are of neurobiological origin beginning before birth or in very early development, related to complex genetics. It is estimated that in about 10% of cases, ASD is associated with another identifiable medical condition, the most common being tuberous sclerosis. Recently, the epidemiology of ASD has been of particular interest. Estimates of prevalence, based on school and state health systems, have skyrocketed, as have demands for services. Genetics of Childhood Disorders: XLII. Autism, Part 1: Diagnosis and Assessment in Autistic Spectrum Disorders