Multi-institutional survey of the Rett syndrome in Japan.

The results of the first multi-institutional survey of the Rett syndrome in Japan are reported. The survey was performed during 1985 and 1986. Eighty-nine cases were collected, of which 54 cases were confirmed to have the Rett syndrome. The ages of the patients ranged between 1 and 26 years. The clinical onsets occurred after 18 months of age in 28 cases, and before the age of one year in 26. No familial cases nor consanguinity was found. The incidence of perinatal abnormalities among the patients was not significantly higher than in other diseases in which no perinatal factors are involved.