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

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).