Subtypes of pervasive developmental disorder: Clinical characteristics

Previous analysis of data from 505 preschool children with disordered communication, falling into the a priori categories of Pervasive Developmental Disorder (PDD), Developmental Language Disorder, and Nonautistic Low IQ, showed that PDD is statistically distinct from nonPDD. Current analyses of the 194 children with PDD also showed the existence of two subgroups within PDD. Children in these two subgroups are sharply divided on the basis of overall cognitive level; children in both groups share major symptom areas, but specific behavioral manifestations differ. Differing developmental trajectories into school age validate the distinction. A clinically usable algorithm for classifying PDD children into the two subgroups, based on social developmental level and degree of social abnormality, is provided. The findings suggest that high- and low-functioning individuals with PDD should be conceptualized as essentially distinct and should be studied separately for etiology, pathophysiology, course, and treatment.