Rett syndrome: a survey of North American patients.

Parents of 63 North American girls with Rett syndrome filled out retrospective questionnaires in a project of the International Rett Syndrome Association, a parent group. No consistent pattern was revealed of possible etiological factors related to environmental insults; however, additional information gathered supported a genetic etiology. The survey included one pair of identical twins and one child with consanguineous parents. There were 46 male sibs and 34 female sibs. These data weigh against any theory relating etiology to a gene on the X chromosome which is lethal to males in utero. Figures were gathered on a number of clinical items. These were: onset of symptoms between 6 and 18 months of age, 83%; autistic withdrawal, 73%; never walked independently, 23%; hyperventilators with abdominal swelling, 63%; night laughter, 83%. The average age of walking of those who walked was 19 months and the average onset of seizure disorders was between 3 1/2 and 4 years of age. This paper ends by discussing the limitations of a parent questionnaire.