The pervasive developmental disorders (PDDs) are characterized by patterns of deviance and delay in social-communicative development in the first years of life, which are associated with restricted patterns of interest or behaviour. The prototypic PDD is childhood autism; other conditions included in the PDD class in ICD-10 include Rett's syndrome, childhood disintegrative disorder, Asperger's syndrome, and atypical autism. Except for one additional category in ICD-10 (hyperkinetic stereotyped movement disorder), the disorders included in ICD-10 and DSM-IV are essentially identical. In this chapter each of these conditions will be reviewed in terms of their clinical features, definition, epidemiology, course, and aetiology; final sections of the chapter address aspects of treatment and prevention for the group of disorders as a whole (Box 9.2.3.1).
