STUDIES ON PHENYLKETONURIA. I. RESTRICTED PHENYLALANINE INTAKE IN PHENYLKETONURIA 1

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Abstract
Phenylalanine deficient synthetic diets, in which the protein component was compounded of pure amino acids, were given to 5 children with phenylketonuria. Their blood levels of phenylalanine decreased to normal over a period of 2 weeks, and their excretion of phenylpyruvic acid and other abnormal metabolites ceased. An amount of phenylalanine sufficient to allow growth, but not enough to cause an increased blood level, was then added to the diet and they were maintained in this state for varying lengths of time. A 4.5 year old girl showed some improvement in behavior, but after 3 months had regressed to her original condition. A 4 year old boy showed considerable improvement in behavior in 3 months. In addition, epileptic seizures were cured and an abnormal ecg became normal at the end of 3.5 months. An 11 month old female phenylketonuric, who appeared to be clinically normal, continued to progress at a nearly normal rate until she was 23 months old. Phenylalanine was returned to her diet, and for the next 15 months she progressed at a much slower rate. An 8 month old boy with a severe convulsive disorder recovered completely from the seizures within a month and developed normally for the following 2 months. A 10 month old girl with severe seizures stopped having outward signs of seizures. Her ecg showed improvement, but retained signs of abnormal electrical activity. None of the cases showed signs of rapid deterioration or rapid loss of gained accomplishments when phenylalanine was returned to their diet, but all manifested a slow regression. All of the observations are consistent with the hypothesis that at least some of the pathological manifestations of phenylketonuria occur as the result of the presence of some substance with a toxic effect on the nervous system.