Autism Related Disorders
Rett syndrome and childhood disintegrative disorder (CDD) are two very rare forms of ASD that include a regression in development. Only 1 of every 10,000 to 22,000 girls has Rett syndrome. Even rarer, only 1 or 2 out of 100,000 children with ASD have CDD.
Unlike other forms of ASD, Rett syndrome mostly affects girls. In general, children with Rett syndrome develop normally for 6–18 months before regression and autism-like symptoms begin to appear. Children with Rett syndrome may also have difficulties with coordination, movement, and speech. Physical, occupational, and speech therapy can help, but no specific treatment for Rett syndrome is available yet.
With funding from the Eunice Kennedy Shriver National Institute of Child Health and Human Development, scientists have discovered that a mutation in the sequence of a single gene is linked to most cases of Rett syndrome. This discovery may help scientists find ways to slow or stop the progress of the disorder. It may also improve doctors' ability to diagnose and treat children with Rett syndrome earlier, improving their overall quality of life.
CDD affects very few children, which makes it hard for researchers to learn about the disease. Symptoms of CDD may appear by age 2, but the average age of onset is between age 3 and 4. Until this time, children with CDD usually have age-appropriate communication and social skills. The long period of normal development before regression helps to set CDD apart from Rett syndrome. CDD may affect boys more often than girls.
Children with CDD experience severe, wide-ranging and obvious loss of previously-obtained motor, language, and social skills. The loss of such skills as vocabulary is more dramatic in CDD than in classic autism. Other symptoms of CDD include loss of bowel and bladder control.