Severe mental retardation in five siblings due to maternal phenyketonuria.

In an epidemiological investigtion of mental retardation in the county of Västerbotten in Sweden the mother of five severely mentally retarded children was found to have untreated phenylketonuria (PKU). None of the children had PKU. The maternal PKU may have been a cause of the mental retardation, retarded intrauterine growth and different types of malformations. There is now an increasing number of girls with PKU in whom dietary treatment has been carried out and already withdrawn. These girls require thorought information on the high risk of serious fetal damage before they become pregnant. Dietary treatment should be introduced before any conception.