Pervasive Developmental Disorders

Under the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5), the umbrella category of Pervasive Developmental Disorders (PDD) has been consolidated into a single diagnosis: Autism Spectrum Disorder (ASD).
Diagnostic terms previously falling under this category, such as Asperger syndrome and Pervasive Developmental Disorder–Not Otherwise Specified (PDD-NOS), are no longer used as independent diagnoses and are now incorporated entirely into the ASD category.

Historically, PDD-NOS was used to define a population that exhibited many symptoms of ASD across multiple developmental domains but did not meet the full criteria for classic autism.
Under the current DSM-5 criteria, individuals previously diagnosed with PDD-NOS are considered to have an ASD.
The clinical presentation in these individuals typically evolves over time; some children may develop more severe ASD symptoms, whereas others may progress and mature without long-term impairments.

The disorders formerly grouped as PDDs (now ASD) represent a category of disability characterized by three cardinal features:
- Social Deficits: Manifestations include poor eye contact, a lack of joint attention (the inability to spontaneously seek or share interests), an inability to form relationships, and a lack of social reciprocity.
- Communication Impairments: Features include delayed language development, limited conversational abilities, echolalia, and the scripting of memorized statements.
- Restrictive, Repetitive, and Stereotyped Patterns: Characteristic behaviors involve motor stereotypies (e.g., hand flapping, spinning, rocking, finger wiggling, and pacing), an insistence on sameness, rigid inflexibility, highly restrictive fixations, and heightened sensory awareness.

No single biological etiology has been identified; rather, the presentation is the end product of a collection of different etiologies that result in a characteristic pattern of atypical development.
The condition is a neurodevelopmental disorder with a high degree of heritability, believed to be genetically based and potentially activated by unknown environmental epigenetic factors.

Association	Clinical Significance
Intellectual Disability	Frequently associated with cognitive impairment, although recent reports suggest the prevalence of concurrent intellectual disability may be as low as 26% to 29% due to better recognition of milder cases.
Seizures	Approximately 25% of affected individuals will develop an associated seizure disorder over their life span.
Sensory Reactivity	Children may overreact or underreact to environmental stimuli (e.g., noise, smells, textures, pain, or touch).
Genetic Syndromes	Often seen as a primary presentation in specific biological conditions, including fragile X syndrome, Rett syndrome, tuberous sclerosis complex, Down syndrome, Angelman syndrome, and Prader-Willi syndrome.