Prenatal Diagnosis of Glycine Encephalopathy

To the Editor: The report by García-Castro et al.* in the January 14 issue describes the prenatal diagnosis of nonketotic hyperglycinemia. In 1979 we diagnosed nonketotic hyperglycinemia in a three-month-old boy presenting with hypotonia, general retardation, and seizures. The diagnosis was confirmed in two other independent laboratories. In December 1980 the mother told us she was pregnant and asked for a prenatal diagnosis. Amniotic fluid was obtained for analysis of free amino acids at 18 weeks of gestation. Amino acid analysis was performed by ion-exchange column chromatography. The concentrations were 419 μmol per liter for glycine and 27 μmol per.