PDD-NOS stands for pervasive developmental disorder not otherwise specified. In essence, it’s a diagnosis that means “on the autism spectrum, but not falling within any of the existing specific categories of autism.”
To explain more fully, there are five disorders that fall under the category of “pervasive developmental disorders” (PDDs). These include autism, Asperger syndrome, Rett syndrome, fragile X syndrome, and PDD-NOS. Autism, Asperger syndrome, Rett syndrome and fragile X are all specifically described in the DSM-IV — the manual that practitioners use to diagnose neurological disorders.
Many children have some symptoms of one PDD and some symptoms of another, but not enough of any one of the four specific disorders to receive a diagnosis. Thus, they do have a PDD — but they do not have Rett syndrome, fragile X, Asperger syndrome, or autism. As a result, they receive the catch-all diagnosis of PDD-NOS.
There is a common belief that the diagnosis PDD-NOS means that a child has, in essence, a touch of autism. In fact, this may be true or untrue. A child may, for example, have only a few mild symptoms of a PDD and still qualify for the PDD-NOS label. On the other hand, he may have very severe delays in language and communication skills, but still not qualify for a specific autism diagnosis.
At present, physicians are not in agreement as to exactly when a child should be diagnosed with PDD-NOS, autism, or Asperger syndrome. As a result, it is very possible for the same child to receive different diagnoses from different physicians while exhibiting exactly the same symptoms.