Pterins analysis in amniotic fluid for the prenatal diagnosis of GTP cyclohydrolase deficiency

Summary Hyperphenylalaninaemia due to tetrahydrobiopterin deficiency is a group of rare and severe diseases. Prenatal diagnosis of dihydropteridine reductase and pyruvoyltetrahydropterin synthetase deficiencies can be achieved by enzyme assay in cultured fluid cells and/or fetal blood. In contrast, prenatal diagnosis of GTP cyclohydrolase deficiency can only rely on the measurement of pterin metabolites in the amniotic fluid.A pregnancy at risk for GTP cyclohydrolase deficiency was investigated. HPLC analysis of amniotic fluid pterins revealed neopterin and biopterin concentrations below the lowest limit of normal age-matched gestations. The mother refused abortion. The early follow-up of the child confirmed the diagnosis of GTP cyclohydrolase deficiency (hyperphenylalaninaemia, abnormal profile of urinary pterins and neurological deterioration).