These pages contain information about pervasive developmental disorder, PDD. The term PDD is widely used by professionals to refer to children with autism and related disorders, but you should be aware that there is a great deal of disagreement, as well as confusion, among the professionals concerning the appropriateness of the PDD label. Until much more is known about the cause of autism, there will continue to be disagreements among the various authorities as to how to diagnose and identify autism and how to label it properly.