No fine motor deficits in patients with untreated non-phenylketonuria hyperphenylalaninaemia.

Twenty-four untreated adolescent and adult patients with non-phenylketonuria (PKU) hyperphenylalaninaemia (HPA) (serum phenylalanine levels < 600 mumol l-1) and 24 healthy controls matched for age, sex and IQ were investigated for their neurological outcome, especially for fine motor abilities by the Motor Performance Task. No pathological findings could be revealed by clinical neurological examination. Patients with HPA and healthy controls did not significantly differ in their fine motor performances. These performances were not significantly influenced by serum phenylalanine concentrations. Our results indicate that untreated patients with non-PKU HPA are not at clinically significant risk for developing fine motor deficits and severe neurological impairment. From this point of view a dietary treatment is not necessary in patients with HPA, as recommended most recently.