Pervasive developmental disorders (PDD) are a group of neuropsychiatric disorder diagnoses. There are five disorders in the group.
The most common of these disorders are Autism, Asperger Syndrome, and Pervasive disorder not otherwise specified (PDD-NOS). These three disorders are also called autism spectrum disorders.
The other two disorders, Rett syndrome and Childhood disintegrative disorder (CDD), are uncommon.
A child's parents might begin to notice signs of PDD when the child is a baby. Symptoms usually appear before the child is three years old.