Rett's syndrome: a progressive developmental disability in girls.

Two girls are described who had normal physical and mental development during the first few months of life, documented on home movies in one. Gross motor development slowed during the second half of the first year followed by loss of acquired vocabulary and deterioration of fine motor skills. Linear growth and head growth decelerated. Stereotyped hand movements appeared around 2 to 3 years of age. Early appropriate social responses faded into a vacant stare. Neurological development was characterized by early hypotonia followed by ataxia and finally spasticity. One girl has been followed through adolescence. Additional symptoms in later childhood and adolescence included scoliosis, episodes of hyperpnea, vasomotor disturbances of the legs, and precocious puberty. The patients fit the criteria for a progressive neurological disorder called Rett's syndrome, which results in profound developmental disability and occurs only in girls. Etiology remains unknown.