Barbara Umbarger

Procedures for monitoring the low-phenylalanine diet in treatment of phenylketonuria

Treatment of phenylketonuria consists of providing an intake of phenylalanine high enough to meet the nutritional needs of a growing child without exceeding his limited capacity to utilize it. This balance can be achieved by considering serum phenylalanine levels, urinary phenylalanine excretion, and urinary orthohydroxyphenylacetic acid excretion in relation to the phenylalanine intake. Practical procedures are recommended for obtaining these data. During periods of febrile illness, phenylalanine deficiency, or phenylalanine excess, characteristic changes occur in the relationships between intake of phenylalanine and the biochemical parameters. Interpretation of these changes is the basis on which dietary alterations are made.

EXCRETION OF PHENYLALANINE BY NORMAL CHILDREN AND BY PATIENTS WITH PHENYLKETONURIA.

Urinary phenylalanine was measured in specimens from 509 normal infants, aged 2 to 6 weeks; from 954 hospital patients, aged 1 week to 16 years; and from 44 phenylketonuric patients. Mean excretion of phenylalanine by nonphenylketonuric children was 24 μg per milliliter (range 0 to 175) and by phenylketonuric patients, 259 μg per milliliter (range 100 to 530). The ranges of phenylalanine excretion overlapped. Two phenylketonuric infants and 2.5 per cent (35) nonphenylketonuric children excreted phenylalanine in the same ranges, 93 to 182 μg per milliliter. In nonphenylketonuric children excretion of phenylalanine greater than 93 μg per milliliter was accompanied by generalized aminoaciduria.