Transitory hyperphenylalaninaemia in children with continuously treated phenylketonuria

Cognitive and behavioral effects of temporarily challenging the CNS with elevated levels of phenylalanine in treated phenylketonuria (PKU) were investigated in a triple-blind, cross-over study. A high phenylalanine supplement was given over 3 months to sixteen 10- to 16-year-old early and continuously treated children with classical PKU. We used the WISC and Rivermead tests to measure cognitive function and the Rutter Scales to assess disordered behavior. Parents and children guessed at the condition imposed. The Group x Phase interaction for phenylalanine level was statistically significant, but this pattern was not mirrored in the psychological test data, and guessing was random. Results suggest that intellectual ability, memory, and conduct are not affected by medium-term hyperphenylalaninaemia in PKU after 10 or more years of treatment.