MILD HYPERPHENYLALANINEMIA AND HETEROZYGOSITY OF THE PHENYLALANINE-HYDROXYLASE GENE

Newborn screening for phenylketonuria (PKU) is now the standard of pra ctice. Initial phenylalanine blood levels of 240 mu mol/L result in re ferral of affected newborns to medical facilities experienced in carin g for patients with metabolic disorders. This case report concerns a f emale infant born in 1976 with a presumptive positive PW screening tes t on the third day of life of 240 mu mol/L phenylalanine. Follow-up le vels while the mother was breast feeding on the sixth day of life were 324 and, on the 27th day, 312 mu mol/L. She was subsequently lost to follow-up at age 11 years, but returned at 19 years of age due to preg nancy, with a blood phenylalanine level of 132 mu mol/L. Mutation stud ies then were performed documenting that she was a carrier for the phe nylalanine hydroxylase gene and did not have hyperphenylalaninemia. Th e mother's parents and the infant were also genotyped confirming heter ozygosity. The infant on follow-up is completely normal, following a n ormal pregnancy. (C) 1998 Academic Press.