PHENYLKETONURIC PATIENTS DECADES AFTER DIET

Nineteen early-treated phenylketonuric patients, whose diet was discon tinued between 4.5 and 13 years of age, and who have been off the diet for 12-28 years, were reassessed in 1992-93. There was little change in mean IQ between end of diet and follow-up, less than one IQ point o n the average, with no change for any individual exceeding 12 IQ point s. Both prior and current IQ correlated slightly negatively with mean phenylalanine (Phe) concentration, and positively with parents' educat ion. The phenylalanine level at follow-up was significantly lower on a verage by about 900 mu mol/L. Five of the subjects (26%) have evidence of mental disease. However, the data suggest that the discontinuation of the diet did not cause intellectual deterioration. Nonetheless, th e patients' intellect cannot be the only consideration for maintenance of diet. The occurrence of psychopathology among phenylketonuric pati ents and the possible unknown effects of toxic elevation of phenylalan ine during their lifetime suggest the need to maintain the diet. The u se of DNA for diagnostic and prognostic purposes might assist in decis ions about dietary quality and duration, and in anticipation of psycho pathology.