Autism: Encyclopedia II - Autism - Other pervasive developmental disorders

Autism - Other pervasive developmental disorders

Autism and Asperger's syndrome are just two of the five pervasive developmental disorders (PDDs). The three other pervasive developmental disorders are Rett syndrome, Childhood disintegrative disorder, and Pervasive developmental disorder not otherwise specified. Some of these are related to autism, while some of them are entirely separate conditions.

Autism - Rett syndrome

Rett syndrome is relatively rare, affecting almost exclusively females, one out of 10,000 to 15,000. After a period of normal development, sometime between 6 and 18 months, autism-like symptoms begin to appear. The little girl's mental and social development regresses; she no longer responds to her parents and pulls away from any social contact. If she has been talking, she stops; she cannot control her feet; she wrings her hands. Some of these early symptoms may be confused for autism. Some of the problems associated with Rett syndrome can be treated. Physical, occupational, and speech therapy can help with problems of coordination, movement, and speech.

Scientists sponsored by the National Institute of Child Health and Human Development have discovered that a mutation in the sequence of a single gene causes Rett syndrome, and can physically test for it with a 80% accuracy rate ^[45]. Rett syndrome in the past was sometimes classified as an autistic spectrum disorder, however most scientists agree that Rett syndrome is a separate developmental disorder and not part of the autistic spectrum ^[46].

Autism - Childhood disintegrative disorder

Childhood disintegrative disorder (CDD, and sometimes abbreviated as CHDD also) is a condition appearing in 3 or 4 year old children who have developed normally until age 2. Over several months, the child will deteriorate in intellectual, social, and language functioning from previously normal behaviour. This long period of normal development before regression helps differentiate CDD from Rett syndrome (and in fact it must be differentiated from autism in testing). The cause for CDD is unknown (thus it may be a spectrum disorder) but current evidence suggests it has something to do with the central nervous system ^{[47] [48]}.

Autism - Pervasive developmental disorder not otherwise specified

Pervasive developmental disorder not otherwise specified, or PDD-NOS, is referred to as a subthreshold condition because it is a classification which is given to someone who suffers from impairments in social interaction, communication, and/or stereotyped behaviour but does not meet the criteria for one of the other four pervasive developmental disorders. Unlike the other four pervasive developmental disorders, PDD-NOS has no specific guidelines for diagnosis, so the person may have a lot of characteristics of an autistic person, or few to none at all. Note that pervasive developmental disorder is not a diagnosis, just a term to refer to the five mentioned conditions, while PDD-NOS is an official diagnosis ^[49].

Adapted from the Wikipedia article "Other pervasive developmental disorders", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki