Problems of prenatal diagnosis of non-ketotic hyperglycinaemia.

Non-ketotic hyperglycinaemia (NKH) is a rare disorder of amino acid metabolism, causing severe, frequently lethal neurological symptoms in the neonatal period. There is no curative therapy, and attempts at prenatal diagnosis have been unsuccessful. In the present study the usefulness of the determination of the glycine/serine ratio in the prenatal diagnosis of NKH was studied. The glycine/serine ratio of the amniotic fluid of the last trimester of pregnancies with a fetus affected with NKH was higher (8.5 +/- 3.3; mean +/- SD) than in pregnancies of NKH-heterozygote mothers with a healthy fetus (4.1 +/- 1.7) or than in pregnancies of healthy mothers (4.3 +/- 1.5). There is, however, overlapping of individual values, which limits the usefulness of this test for prenatal diagnosis of NKH.