A progressive neurogenetic disorder with onset in the first few years of life, and for which the first sign is usually hypotonia (a loss of muscle tone). Characterized by stunted development, a lag in brain and head growth, loss of purposeful hand use and a number of major neurological problems, including epilepsy and decreased mobility involving gait abnormalities. Also presents as a diminished ability to express feelings and avoidance of eye contact. Unlike most genetically based disorders, it is almost exclusively restricted to females and associated with mutation of MECP2-gene on X chromosome in the majority of cases. Both its incidence and prevalence are 1 in 10,000 to 15,000 live births.
See Hypotonia, MECP2 gene, Syndrome