Both affect so few children that they will not be considered here. The pervasive developmental disorders also include Rett’s disorder, a neurological condition, and childhood disintegrative disorder, a poorly defined variant of autism.
The latter is a term for atypical autism, that is, either milder symptoms or characteristics in only one or two of the three areas necessary for a diagnosis. In the Diagnostic and Statistical Manual of Mental Disorders IV-TR (DSM-IV-TR), pervasive developmental disorder is the umbrella term covering autistic disorder, Asperger’s disorder, and pervasive developmental disorder NOS (not otherwise specified). The definition of autism has evolved over the years and was broadened with the introduction in the 1980s of the terms pervasive developmental disorder and Asperger syndrome. Autism is a behavioral syndrome characterized by a triad of impaired social interaction, communication, and imaginative development, with repetitive stereotyped behaviors.
