It is also known as atypical autism.

Pervasive developmental disorder or PDD - also known as atypical autism.

These include PDD 'not otherwise specific' (including 'atypical autism'), as well as Rett syndrome and Childhood disintegrative disorder (CDD).

ASDs include autistic disorder, pervasive developmental disorder - not otherwise specified (PDD-NOS, including atypical autism), and Asperger syndrome.

To further complicate the issue, PDD-NOS can also be referred to as "atypical personality development", "atypical PDD", or "atypical Autism".

PDD-NOS is considered "subthreshold autism" and "atypical autism" because it is often characterized by milder symptoms of autism or symptoms in only one domain (such as social difficulties).

PDD-NOS is often called atypical autism, because the criteria for autistic disorder are not met, for instance because of late age of onset, atypical symptomatology, or subthreshold symptomatology, or all of these.

Advances in genetic technology allow clinical geneticists to link an estimated 40% of ASD cases to genetic causes; in one study the diagnostic yield for AS, PDD-NOS and atypical autism was similar to that for classic autism.

Catherine Rice: When we say children are identified with ASD or autism spectrum disorder, we include what's typically the three primary Autism Spectrum Disorders: autistic disorder, Asperger's disorder and atypical autism or pervasive developmental disorder not otherwise specified.