Differential diagnosis of PDDNOS in children

PDDNOS is a particularly important form of autism spectrum disorder (ASD) due to the frequency with which it is diagnosed. Having said that, it is often diagnosed by what it is not (not autism) as opposed to what it is. And, while PDDNOS is likely to be more common than autism, studies on PDDNOS are much less frequent. Perhaps with the exception of childhood degenerative disorder, PDDNOS has less diagnostic research on it than any other ASD. The purpose of the present paper was to review the available research on the definition and diagnosis of PDDNOS. The data are analyzed and future goals for conceptual and diagnostic research are discussed with the idea of further enhancing a neglected diagnostic category.