Social quotients of children with phenylketonuria before and after discontinuation of dietary therapy.

The records of 16 early-treated children with phenylketonuria (PKU) whose low-phenylalanine diets had been discontinued at an average age of 5.5 years were reviewed for evidence of deterioration in functioning. Measures of their medical and social status, namely, serum phenylalanine levels and Vineland Social Quotients, before and after diet discontinuation were investigated via repeated measures analyses of variance. Social quotients decreased significantly following discontinuation and were inversely correlated with serum phenylalanine levels.