Phenylketonuria: diet for life or not?

In order to evaluate the argument whether or not a restricted phenylalanine diet should be maintained for life in patients with phenylketonuria (PKU), 16 patients with early treated PKU but off diet since their 11th birthday were investigated. The evaluation included a detailed neurological examinat ion, IQ, neurophysiological testing and MRI of the brain. Even if IQ and el ectrophysiological studies were normal or unchanged if compared to results before diet discontinuation, all patients revealed abnormal neurological si gns. We conclude that the diet should be continued during adult life, but s omewhat higher phenylalanine levels (<10 mg/dl; <600 mu mol/l) than at youn ger ages should be allowed.