Autism Spectrum Disorders page 2

Pervasive Developmental Disorder, Not Otherwise Specified (PDD-NOS)

This mouthful of a diagnosis applies to most children with autistic spectrum disorder. Children whose autism is more severe than Asperger's syndrome but not as severe as autistic disorder are diagnosed with PDD-NOS.

Autism symptoms in kids with PDD-NOS vary widely, making it hard to generalize. Overall, compared to children with other autistic spectrum disorders, children with PDD-NOS have:

• Impaired social interaction (like all children with autistic spectrum disorder)
• Better language skills than kids with autistic disorder but not as good as those with Asperger's syndrome
• Fewer repetitive behaviors than children with Asperger's syndrome or autistic disorder
• A later age of onset

No two children with PDD-NOS are exactly alike in their symptoms. In fact, there are no agreed-upon criteria for diagnosing PDD-NOS. In effect, if a child seems autistic to professional evaluators but doesn't meet all the criteria for autistic disorder, he or she has PDD-NOS.

Autistic Disorder

Children who meet more rigid criteria for a diagnosis of autism have autistic disorder. They have more severe impairments involving social and language functioning as well as repetitive behaviors. Often, they also have mental retardation and seizures.

Rett Syndrome

Almost exclusively affecting girls, Rett syndrome is rare. About one in 10,000 to 15,000 girls develop this severe form of autism. Between 6 and 18 months of age, the child stops responding socially, wrings her hands habitually, and loses language skills. Coordination problems appear and can become severe. Head growth slows down significantly and by the age of two is far below normal.

Rett syndrome is usually caused by a genetic mutation. The mutation usually occurs randomly, rather than being inherited. Treatment focuses on physical therapy and speech therapy to improve function.

Childhood Disintegrative Disorder

The most severe autistic spectrum disorder, childhood disintegrative disorder (CDD), is also the least common.

After a period of normal development, usually between age 2 and 4, a child with CDD rapidly loses multiple areas of function. Social and language skills are lost as well as intellectual abilities. Often, the child develops a seizure disorder. Children with childhood disintegrative disorder are severely impaired and don't recover their lost function.

Fewer than two children per 100,000 with an autistic spectrum disorder meet criteria for childhood disintegrative disorder. Boys are affected by CDD more often than girls.