Adjustment and intelligence among children with phenylketonuria in Sweden

In this investigation we present a recent survey of treatment effects among 8 to 19-y-old Swedish children and youths with phenylketonuria (PKU). The results from intelligence tests and a questionnaire comprising four scales, work capacity, social competence, and internalising and externalising problems, were used. Severity of disease, early treatment, and contemporary phenylalanine levels were assessed. The results showed that development of the patients' intelligence was normal. Adjustments were rated by the patients, their parents and their teachers, and the results were compared with those of a healthy reference group. The PKU patients did not differ from the reference group except for externalising problems judged by the children themselves. None of the patients with PKU showed signs of externalising problems in contrast to the reference group, where such behaviour was observed. Patients with severe PKU, however, showed less social competence compared with patients with a milder form of the disease, according to their own and their parents' ratings. Phenylalanine level in blood tests was in accordance with treatment norms, although the teenagers had higher levels of phenylalanine than the younger patients. Conclusion: Normal intelligence and adjustment is found among patients with PKU when plasma phenylalanine levels are within treatment norms.