Do adult patients with phenylketonuria improve their quality of life after introduction/resumption of a phenylalanine-restricted diet?

Aim: To evaluate the possible influence of dietary treatment on the quality of life of adult patients with PKU (phenylketonuria) following late introduction or resumption of a Phe-restricted diet. Methods: Fifteen adult patients with classical PKU (10F, 5M; mean age: 27.5 y, range: 16.4–37.5 y) were selected for the study. These patients had either resumed a restricted diet after a period of discontinuation, or were placed on a restricted diet after late diagnosis. All of them were interviewed about their quality of life using a 24-item questionnaire. Results: The index of dietary control was poor (median Phe: 954 μmol/L) in 8/15 patients, regular (Phe: 514 μmol/L) in 4/15 and good (Phe: 354 μmol/L) in 3/15 patients. Fifty-three percent of patients reported that their state of health was very good, 47% described it as good, and 40% felt that their present health on-diet was better than it had been off-diet; 53% believed that they were calmer, quieter and less easily upset and 40% were more alert and were more able to maintain attention while on-diet. Thirty-three percent of the patients felt happier, and 27% felt more vital; 20% thought that they were less impulsive and aggressive, and that they were now less argumentative than before. Sixty percent of the patients felt that their quality of life had improved on-diet compared with the situation off-diet. Conclusion: More than half of our patients believed that their quality of life improved with a Phe-restricted diet; they reported feeling calmer, quieter, and less easily upset. Only 47% attained regular to good dietary control.