Autism spectrum disorder includes autism (autistic disorder), pervasive development disorder not otherwise specified (PDD-NOS) Asperger syndrome, childhood disintegrative disorder and Rett syndrome.
In the United States, PDD-NOS is currently the most frequent diagnosis of autistic spectrum disorder (1). PDD-NOS will no longer be listed separately from autism spectrum disorder in DSM-5, bringing all diognoses within ASD.
The latest CDC prevalence report lists the following diagnostic breakdown (in Table 3):
Autistic – 1,158 (44%)
PDD-NOS – 1,230 (47%)
Asperger – 239 (9%)
TOTAL – 2,627
(1) Prevalence of Autism Spectrum Disorders – Autism and Developmental Disabilities Monitoring Network, 14 Sites, United States, 2008 Surveillance Summaries. March 30, 2012 / 61(SS03);1-19.