Autism is a general term used to describe a group of complex developmental brain disorders known as Pervasive Developmental Disorders (PDD). The other pervasive developmental disorders are PDD-NOS (Pervasive Developmental Disorder – Not Otherwise Specified), Asperger’s Syndrome, Rett Syndrome and Childhood Disintegrative Disorder. Many parents and professionals refer to this group as Autism Spectrum Disorders.
Autism Speaks, “What is Autism?” http://www.autismspeaks.org/whatisit/index.php
Classic Autism (also known as Autistic Disorder) is an Autism Spectrum Disorder (ASD). It is generally classified by impairment in social interactions and communication and includes some restrictive or repetitive behaviors.
Here is a link to DMS-IV Diagnostic Criteria to Autistic Disorder http://www.cdc.gov/ncbddd/autism/hcp-dsm.html
Pervasive Developmental Disorder (PDD-NOS) – Also called “Atypical Autism”, and it’s a diagnosis that means “on the autism spectrum, but not falling within any of the existing specific categories of autism.” Children with this disorder have many of the same characteristics of Autism, but not all the criteria associated with Autism. It is referred to children who have significant problems with communication and play, and some difficulty interacting with others, but are too social to be considered autistic.
High-functioning autism is at one end of the ASD spectrum. Signs and symptoms are less severe than with other forms of autism. In fact, a person with high-functioning autism usually has average or above average intelligence. The differences from other forms of autism have led many psychiatrists to consider high-functioning autism as similar to or the same as Asperger’s syndrome.
Asperger’s syndrome is a developmental disorder that affects a person’s ability to socialize and communicate effectively with others. Children with Asperger’s syndrome typically exhibit social awkwardness and an all-absorbing interest in specific topics. The essential features of Asperger’s syndrome are severe social interaction impairment and restricted, repetitive patterns of behavior and activities. It is similar to autism, but children with Asperger’s do not have the same difficulties in acquiring language that children with autism have.
Rett syndrome is a rare genetic disorder that affects the way the brain develops. It occurs almost exclusively in girls. Most babies with Rett syndrome develop normally at first, but symptoms start to surface after 6 months of age. Over time, children with Rett syndrome have increasing problems with movement, coordination and communication that may affect their ability to use their hands, communicate and walk. A brief autistic-like phase may be observed during the preschool period, but the subsequent course and clinical features are markedly different from autism.
Childhood Disintegrative Disorder, also known as Heller’s syndrome, is a condition in which children develop normally until ages 2 to 4, but then demonstrate a severe loss of social, communication and other skills. Childhood Disintegrative Disorder is very much like autism. Both are among the group of disorders known as pervasive developmental disorders, or autism spectrum disorders. And both involve normal development followed by significant loss of language, social, play and motor skills. However, Childhood Disintegrative Disorder typically occurs later than autism and involves a more dramatic loss of skills. In addition, Childhood Disintegrative Disorder is far less common than autism.