Termination of dietary treatment in phenylketonuria.

Abstract

The aim of this study was to evaluate the influence of early termination of dietary treatment in phenylketonuria by following the patients' mental development. Three groups of patients have been evaluated: Group I — 22 classical PKU cases with a mean treatment period of 4 years and 8 months; Group II — 10 cases of classical PKU with a mean treatment period of 2 years 4 months; Group III — 5 PKU variants treated on average for 3 years and 8 months. The mean period of observation after dietary discontinuation was form 4 to 6 years. Evaluation of development and further progress of PKU patients after terminating the diet was based on the following parameters: clinical symptoms, selected biochemical examinations, scores of mental development, behaviour and school achievements, and EEG examination. Detailed analysis of the data revealed a direct relationship between the long-term results of treatment and the age of starting treatment, even in the range of the first three months of life, and also the quality of dietary control and the period of treatment. Three significant changes emerged after discontinuation of the diet: 1) Decreasing intelligence quotients in most patients with classical PKU. 2) Difficulties in adaptation and school achievements in these patients. 3) Large number of EEG abnormalities after termination of the diet. These findings in classical PKU patients after discontinuation of the diet reveal that 5 year's dietary treatment is too short for effective therapy in classical PKU. Normal mental development and good school achievements in PKU variants (hyperphenylalaninaemia) with a treatment period of 31/2 years suggest that in this condition the period of dietary treatment can possibly be shorter than in classical phenylketonuria.