Long-term follow-up of a patient with mild tetrahydrobiopterin-responsive phenylketonuria

We report on the long-term follow-up of the first Italian patient with the tetrahydrobiopterin (BH4)-responsive type of phenylalanine hydroxylase deficiency (R243X/Y414C genotype). The patient was diagnosed by the newborn screening for phenylketonuria (PKU) and with a positive BH4 loading test. Introduction of BH4 (initially 10 and later 20 mg/kg/day) in addition to reduced low-phenylalanine diet resulted in therapeutic plasma phenylalanine concentrations (<340 mumol/L). Very good compliance and no side effects in this patient demonstrate the great potential of BH4 in the treatment of some patients with mild PKU. (C) 2003 Published by Elsevier Inc.