In an earlier paper two of us (F. A. H. and C. W. S.) presented the short-term psychological and behavioral changes observed in two preschool phenylketonuric children treated with a phenylalanine-restricted diet.1 In addition, a newborn sibling of one of the cases, who had received dietary treatment since 8 weeks of age, was reported as developing normally through the first 9 months of life. The present paper offers an additional year of follow-up on these three patients. It also reports on the changes observed in a second newborn and two 18-month-old children under long-term therapy.
The phenylalanine-restricted diet used in this series is that outlined by Armstrong and Tyler.2,3 Patients are given a phenylalanine-free diet consisting of a protein hydrolysate basal mix* (4.2 gm/kg/day), fat in the form of a vegetable oil (3.0 gm/kg/day) and CHO (10 gm/kg/day) for three weeks. On such a diet