Rett Syndrome

Overview, Causes, & Risk Factors

Rett Syndrome is a severe progressive neurological disorder that causes marked developmental regression, especially in the areas of expressive language and hand use. It occurs only in girls.

The gene associated with this disorder was recently identified on the X-chromosome. This gene encodes methl-CpG-binding protein 2 (MeCP2), which regulates synthesis (transcription) of various other proteins.

Synthesis of incorrect proteins, due to mutations in the gene, causes damage in the maturing brain. The severity of the disease is linked to specific types of mutation.

Rett Syndrome has an estimated prevalence of seven to ten cases per 100,000 females. Females have two X chromosomes, so even when one has this significant mutation, the other X chromosome provides enough normal protein for the child to survive.

Males conceived with this mutation are miscarried (spontaneously aborted) during pregnancy because they do not have a second X chromosome to compensate for the problem.

Most cases (99.5%) are due to spontaneous mutations, rather than inheritance. However, the incidence of familial cases is higher than would be expected by chance, so there may be an inherited factor involved.