Mental development of phenylketonuric children on or off diet after the age of six

Abstract

Eleven children with phenylketonuria (PKU) taken off diet after the age of six showed significant decreases in rate of mental development compared with 26 control children children of comparable IQ and with 17 PKU children of comparable IQ who remained on the diet. Changes in rate of mental development were significantly and inversely correlated with plasma phenylalanine levels in treated PKU.