Pervasive Developmental Disorder - Not Otherwise Specified (PDD-NOS) is one of the pervasive developmental disorders and autism spectrum disorders.

PDD-NOS is a diagnosis for people who are well-described by the "PDD" label, but cannot be categorized by any other disorder. It is usually milder than autism and has similar symptoms to autism, with some symptoms present, and others absent^...This disorder is sometimes called "atypical autism" by autism specialists. The boundaries between PDD-NOS and non-autistic conditions are not fully resolved.   Louis J. Sheehan, Esquire