About Rett Syndrome
Rett syndrome is a clinically-defined neurologic disorder, typically seen in females, which is associated in most cases with sporadic mutations in the coding region of the transcriptional regulator MeCP2. Rett syndrome occurs in a variety of racial and ethnic groups worldwide with estimates between 1:10,000-1:23,000 female births; however, the incidence may be greater as genetic evidence accumulates and the clinical spectrum of the disorder is re-evaluated. The clinical manifestations of Rett syndrome are variable and dynamic; development appears normal until 6-18 months of age, followed by slowing of head growth, loss of acquired speech and hand skills, gait abnormalities, and development of stereotyped repetitive hand movements. The latter may change over time and consist of hand washing, hand wringing, hand tapping, hand clapping, and hand mouthing. Other frequent manifestations include breathing irregularities (hyperventilation and apnea), seizures, teeth grinding, and scoliosis. Depending on the clinical presentation, cases of Rett syndrome are labeled as classic or atypical (several types). The almost exclusive presentation of Rett syndrome in females has been attributed to the X-linked nature of the disorder that leads to lethality in male fetuses, while its phenotypical spectrum is associated with the variable inactivation of the X chromosome carrying the mutated allele. However, many questions remain in Rett syndrome since correlations between genotype and phenotype are limited. In as many as one-third of patients, no mutation in the coding region of MeCP2 is detected. Conversely, MeCP2 mutations are seen occasionally in patients with other neurologic manifestations. The impact of the type of mutation or location within the MeCP2 gene on the severity of Rett syndrome is still under active investigation.