The various autism spectrum disorders include autistic disorder, Asperger's syndrome, pervasive developmental disorder, Rett syndrome and childhood disintegrative disorder, according to WebMD. These are the only subtypes of autism recognized by the Diagnostic and Statistical Manual for Mental Disorders version 5, the most recent edition as of 2015.
Autistic disorder is characterized by problems with social interaction, communication and imaginative play in children under 3 years, confirms WebMD. Affected individuals may have difficulty understanding the thoughts and feelings of others, so they have trouble expressing themselves. Individuals with Asperger's syndrome score well on intelligence tests and have no language deficiencies, but they may have a limited range of interests and social deficiencies. Pervasive developmental disorder, or atypical autism, is characterized by a range of exhibited autistic behaviors that don't fit into a single category from the autism spectrum.
Rett syndrome is often characterized by severe cognitive impairment, according to WebMD. Children with Rett syndrome begin to exhibit repetitive hand movements by age 1 to 4. Despite seemingly normal development, social skills and communication skills begin to decline. Childhood integrative disorder is an extremely rare and debated form of autism in which children lose a portion or all of their social and communication skills after developing normally for at least 2 years.