The offspring of a phenylketonuric couple.

Biochemical studies carried out in seven members of a family with five phenylketonuric subjects are described. The concentration of phenylalanine and the phenylalanine/tyrosine ratios in the blood, together with the values obtained from the L-phenylalanine loading tests, were the criteria used to establish the diagnosis. The results suggest that the non-consanguineous parents, the children and their maternal aunt are homozygous for classical phenylketonuria; the paternal grandmother, as expected, was found to be heterozygous for this metabolic disorder. The mother, diagnosed in the fifth month of her last pregnancy, was treated with a low phenylalanine diet until delivery. Nevertheless, the girl who was born from that pregnancy showed some symptoms resulting from "maternal phenylketonuria", being diagnosed as phenylketonuric at one week of age and treated with a low phenylalanine diet thereafter.