[Phenylalanine-fetopathia in twins of an undiagnosed phenylketonuric mother (author's transl)].

A case report of microcephalic twins born to a hithertoo undedected phenylketonuric mother is given. The female twin suffered from phenylketonuria, too. The clinical findings included microcephaly, growth retardation, retarded bone age and an unusual facies. The psychomotor development was retarded in both twins, but more so in the phenylketonuric twin despite appropriate low phenylalanine diet.