Many people do not know that Autism is actually just one disorder on an entire spectrum of disorders that fall under the category of Autism Spectrum Disorders.
The names of each disorder on the spectrum as well as a comparison of them is listed in the answer. The comparison includes such information as onset, social deficits, communication issues, and behavioral characteristics associated with each of the disorders.
Autism Spectrum Disorders are made up of 5 different disorders that fall under the category.
Here is a comparison of the different disorders and their characteristics:
Onset: Age 3
Social Deficits: eye contact, autistic aloness, peer relationships, lack of social reciprocity
Communication: echoloalia, lack of development of functional speech (50% of group), no speech development, ...