Dr. Jeffrey L. Neul responds:

Rett syndrome is a childhood neurodevelopmental disease that mostly affects girls and is characterized by loss of spoken language and hand use. After normal development, there is gradual regression of mental and physical abilities, usually between six and 18 months of age. Many children become socially withdrawn, avoid eye contact, and dislike being held. After the regression period, these children often regain interest in social interaction.

Eye contact returns as a form of communication. But children with Rett syndrome may also develop repetitive hand movements, such as hand wringing or clapping, that remain after the regression period. They may have difficulty walking, abnormal breathing patterns, and an increased risk of developing seizures. A mutation in a specific gene, MECP2, is found in the majority of Rett syndrome cases.

Autism is more common in boys. It is also characterized by impaired social interaction and communication, but autistic children often do not regain interest in interaction. A small number of people with autism also have a mutation in MECP2.

Neither disorder has a cure. Treatments for both are focused on symptoms, such as improving social interaction in autism and treating seizures in Rett syndrome.