[Rett syndrome: a progressive neurological syndrome in girls].

Rett syndrome, named after Rett's first description in 1966, evolves typically in 3 stages: after normal early psychomotor development up to the age of 6-24 months, stagnation and regression occur over a few months resulting in severe dementia, loss of speech, of social response and of purposeful hand use. This is accompanied by particular stereotyped hand movements and usually also by deceleration of head growth. The further course is often stable for a prolonged period, or only slowly progressive. Common features are seizures, episodic hyperpnea, scoliosis, spasticity and vasomotor disturbances of lower limbs. Rett syndrome has been observed only in girls, all cases (with 2 exceptions) being sporadic. This is probably explained by a X-linked dominant new mutation lethal in males. The pathogenesis is still unknown: no consistent metabolic, morphologic or neuroradiologic abnormalities have been found. According to some epidemiologic investigations, Rett syndrome affects about 1:15,000 girls and is thus responsible for a considerable proportion of severely retarded girls. Within one year the authors have retrospectively diagnosed 15 cases, which is assumed to represent only about a third of patients in Switzerland.