THE PHENYLALANINE RESPONSE CURVE IN RELATION TO GROWTH AND MENTAL-DEVELOPMENT IN THE FIRST YEARS OF LIFE

Thirty-three children with classical phenylketonuria were treated from 9 to 21 days of age onward. The standard for phenylalanine concentrat ion was 0.2-0.5 mmol/l. During the first years of life phenylalanine c oncentrations were measured once every two to six weeks. For each chil d these values were graphically plotted in a so-called phenylalanine r esponse curve. Growth and mental development indices were assessed at about one and two years of age. Measurements for weight, height and he ad circumference were normal at one month of age, showed a significant decline at the age of one year but were restored for normal values at the age of two. No associations were found with phenylalanine paramet ers. Mental development indices at one and two years were not differen t from normal. Significant negative correlations were found between me ntal development indices at one year and phenylalanine values above 0. 5 mmol/l. Changes in mental development indices between the first and second years of life are significantly related to the phenylalanine le vels during the second year of life.