Front Matter

64 What is Autism?

Autism symptoms in children with PDD‐NOS vary widely, making it hard to

generalize. Overall, compared with children with other ASDs, children with

PDD‐NOS have:

● Impaired social interaction (like all children with ASD)

● Better language skills than children with autistic disorder but not as good as

those with Asperger syndrome

● Fewer repetitive behaviors than children with Asperger 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 does not 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 retar-

dation and seizures.

Rett Syndrome

Almost exclusively affecting girls, Rett syndrome is rare. About one in 10,000–

15,000 girls develop this severe form of autism. Between 6 months 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 in the X‐chromosome

gene called MECP2 [23]. 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 ASD, childhood disintegrative disorder (CDD), is also very

uncommon.