[Psychometry and psychological observations in early treated children with phenylketonuria (PKU) during 12 years (author's transl)].

Among 81 PKU's uncovered until 1978/12/31 63 were 1 to more than 8 years old so at least once up to 4 times psychometrically examined. Although the IQ's at 8 years were still in the normal rang there was a slight but between 6 and 8 years statistically significant (p less than 0.01) decline in IQ. There is no correlation between this decline and the diet introduction age (26--29, average 26,4 days) nor the diet discontinuation age (4 to 8 years) and the predominantly good diet quality. But there were relations to the 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. Also the slight but statistically significant IQ deficits demonstrated in heterozygotes for PKU (parents) arise almost entirely from the verbal quotient. It is supposed that both observations are phenylalanine blood level independent phenomena. The demonstration of statistically highly significant augmentations of intracellular phenylalanine (and tyrosine) in heterozygotes and homozygotes for PKU may indicate an explanation. Our 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.