Previous disorders that now fall under the umbrella diagnosis of ASD include the following:
Pervasive Developmental Disorder (PDD)
PDD is called atypical autism. This is a type of catch-all classification for kids who have autistic behaviors but who do not fit cleanly into other categories.
This is what the majority of people think when they hear the term “autism.” It refers to problems having to do with communication, social interactions, and imagination in very young children.
Childhood Disintegrative Disorder
These kids develop like most children for two years and then suddenly lose some or most of their social and communication skills. This is a very rare disorder and its classification as a different condition is a cause of contention among several mental health professionals.
These kids do not have a problem with language. Though they usually score in the average or above average range on intelligent tests, they have the same social challenges and limited scope of interests as children with autistic disorder.