EARLY-TREATED PHENYLKETONURIA - ADULT NEUROPSYCHOLOGIC OUTCOME

Twenty-five adults with phenylketonuria that was treated early were co mpared with 15 unaffected control siblings with respect to intellectua l and neuropsychologic measures. Patients were found to have normal in telligence but were significantly lower than their control siblings on measures of intelligence, attention, and complex visuoconstructional ability. Stepwise multiple regression analyses found the patients' int ellectual outcome to be best predicted by indexes reflecting early ins ult to the brain, whereas performance on a measure of novel problem so lving was best predicted by concurrent serum phenylalanine level. Diff erent pathophysiologic mechanisms may thus account for cognitive defic its in this population. These results provide further evidence of cont inuing benefits of dietary adherence into adulthood.