Facts First
Pervasive Developmental Disorder (PDD) - Not Otherwise Specified (NOS) is a category within the Pervasive Developmental Disorder Umbrella. When a child's problems or diagnostic features do not completely or accurately fit into any one of the other PDD categories (Autistic, Asperger's, Rett's, or Child Disintegrative Disorders) a diagnosis of PDD-NOS is appropriate.
This category should be used when there is a severe and pervasive impairment in the development of reciprocal social interaction associated with impairment in either verbal or nonverbal communication skills or with the presence of stereotyped behavior, interests, and activities.