Reinstitution of diet therapy in PKU patients from twenty-two US clinics.

In a nationwide survey we found 72 PKU (phenylketonuria) patients who had terminated diet but later returned to diet. Sixty-one patients resumed diet due to clinical problems. Age at initial diet discontinuation ranged from three to 20 years. The most prevalent problems reported were poor school performance, and mood and/or behavior changes. Following diet reinstitution, only positive changes were noted for 42 patients, no changes for 19 patients, and 11 had one or more negative changes. Improvements and blood phenylalanine levels were not significantly correlated, but only 11 patients maintained levels less than 10 mg/dl. The number of improvements was significantly correlated with length of time on diet (p less than 0.001). After a median of 10 months on diet, 22 patients had again discontinued due to poor diet control, lack of motivation, poor formula tolerance, lack of apparent benefits and/or changes for the worse. Median time on diet for the 50 second-time continuers was two years nine months.