Background: Discontinuation of dietary therapy in adults with phenylketonuria can lead to neuropsychological abnormalities and emotional problems. The aim of our study was to assess the change in quality of life in adult patients returning to the diet and to define the reasons for failure in diet resumption.
Methods: Quality of life was assessed by means of the Psychological General Well-Being Index before study entry and subsequently after 3 and 9 months. Reasons for failure in diet resumption were analysed.
Results: 53 patients participated in the study. Initial quality of life assessment revealed severe distress in 17%, moderate distress in 28% and positive well-being in 55% of them. In the majority of patients with severe or moderate distress, improvement of subjective well-being was observed (especially in the domains of anxiety and depressiveness) if they managed to return to the diet (blood phenylalanine concentrations before study entry 0.78-1.62 mmol/L, mean 1.16 mmol/L; average blood phenylalanine concentration decrease by 0.42 mmol/L). Only 29 persons managed to maintain the diet for at least 3 months and only 10 participants finished the entire 9-month study protocol. Problems with dietary treatment while at work, the high cost of low-protein products and poor knowledge regarding proper diet were the most important factors responsible for failure in resumption of diet.
Conclusion: Interpersonal differences exist between adult patients on relaxed diet, in some of whom quality of life often remains good, while others can suffer from severe emotional distress. Returning to diet increases quality of life in the majority of patients.