Rett syndrome
a genetic disorder that occurs almost exclusively in female children who develop normally in early infancy but then, between 6 and 18 months of age, undergo rapid regression in motor, cognitive, and social skills; these skills subsequently stabilize at a level that leaves the child with intellectual disability. Symptoms generally include loss of language skills, hand motion abnormalities (e.g., hand wringing, other repetitive, purposeless movements), learning difficulties, gait disturbances, breathing problems, seizures, and pronounced deceleration of head growth. See autism spectrum disorder. [first described in 1966 by Andreas Rett (1924–1997), Austrian pediatrician]