pervasive developmental disorder not otherwise specified

pervasive developmental disorder not otherwise specified (PDD-NOS), condition characterized by impairment in the ability to interact with others and by atypical communication or behavior patterns and interests. In the Diagnostic and Statistical Manual of Mental Disorders-IV (1994; DSM-IV), pervasive developmental disorder not otherwise specified (PDD-NOS) was classified as an autism spectrum disorder (ASD) and was described as atypical autism, because individuals with the disorder exhibited some but not all of the symptoms associated with autism (sometimes called classic autism). Likewise, “not otherwise specified” indicated that an individual’s symptoms were nonspecific, meaning that they differed from symptoms characteristic of certain other childhood developmental disorders, such as Rett syndrome and childhood disintegrative disorder. In 2013, with the release of the DSM-V, PDD-NOS was incorporated into ASD, in a single diagnosis, thereby rendering a diagnosis of PDD-NOS obsolete.

Historically, PDD-NOS affected boys four times more often than girls. The overall prevalence of the disorder was unclear because of the varying clinical definitions used for diagnosis. Many children who had only several symptoms of an autism-like condition, which prevented a definitive diagnosis of autism, were often diagnosed instead with PDD-NOS. Symptoms associated with PDD-NOS appeared after age three, and the pattern in which symptoms manifested and the behaviors displayed by affected children varied widely. Most children with the disorder appeared to develop normally in the first several years of life and then experienced an unusual delay in the development of social abilities. It was usually at this point in the child’s development when other features of PDD-NOS became apparent. These features included gaze avoidance, lack of expressive facial responses, irregularities in speech, repetitive and obsessive behaviors, and delayed development of motor skills. The incidence of severe intellectual disability in PDD-NOS patients was low relative to other developmental disorders.

Although the precise cause of PDD-NOS was unknown, abnormalities in certain structures and in neuronal signaling pathways in the brain have been implicated. Researchers suspected the involvement of underlying genetic defects as well. Treatment for PDD-NOS consisted primarily of behavioral therapy, though some children required the administration of medications to stabilize mood or behavior.