Psychometrie und psychologische Verlaufsbeobachtungen an 63 frühbehandelten Kindern mit Phenylketonurie (PKU)

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Abstract
Among 81 PKU (phenylketonuria) patients examined through 31 Dec. 1978, 63 were 1-8 yr old so that they were psychometrically examined about 4 times. Although the IQ at 8 yr were still in the normal range there was a slight but statistically significant (P < 0.01) decline in IQ between 6-8 yr. There is no correlation between this decline and the diet introduction age (26-29, average 26.4 days) nor the diet discontinuation age (4-8 yr) and the predominantly good diet quality. But there were relations to parental IQ. It seems remarkable that the centers of London and Warschau report declines of the same extent at approximately the same ages in spite of different diet discontinuation ages. The IQ losses in the patients derive almost totally from losses in the verbal part of the tests. The slight but statistically significant IQ deficits demonstrated in heterozygotes for PKU (parents) arise almost entirely from the verbal quotient. Apparently, both observations are phenylalanine blood level independent phenomena. The demonstration of statistically significant augmentations of intracellular phenylalanine (and tyrosine) in heterozygotes and homozygotes for PKU may indicate an explanation. The early treated children with PKU show the same weakness in concentration, perseverance and cognitive abilities (mathematics, orthography, picture coordination) as observed by other centers. These disabilities are largely IQ independent, influence school work adversely but can be improved by psychological promotion. Children with hyperphenylalaninemia do not show the slight decline in IQ nor the specific disabilities.

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