Maternal phenylketonuria.

A mother with phenylketonuria and hyperphenylalaninaemia of 960 mumol/L with four intellectually deficient offspring is described. In addition a mother with hyperphenylalaninaemia of 2100 mumol/L and two intellectually deficient microcephalic children is described. None of the affected children exhibited elevations of blood phenylalanine. In utero phenylalanine toxicity was considered a factor causing the handicaps.