FALSE POSITIVE PRENATAL DIAGNOSIS OF GALACTOSEMIA

Amniotic fluid (AF) was obtained at 18 weeks gestation from a woman who had previously given birth to an infant with galactosemia. The AF cells were cultured and examined for activity of galactose-1-phosphate uridyl transferase (transferase) by UDPG consumption assay. No activity was detectable as compared to activities of 30.8 and 56.0 μmoles UDPG consumed/hr/109 cells in two AF cell control lines. After term delivery the infant was found to be heterozygous for galactosemia with erythrocyte transferase activities of 11.8 and 10.8 μmoles UDPG consumed/hr/gm Hb (nl 22 ± 3.7). He had normal galactose tolerance to milk ingestion. The AF cells from the proband were recultured and again had no detectable transferase activity by consumption assay. However, activity was detectable (2.4 μmoles UDPGal formed/hr/109 cells; nl 2.0 - 24.8) by a radioactive method. These same cells had normal galactokinase activity (1.32 mU/hr/109 cells; nl 0.61 - 1.30). The AF cell line from the proband most resembled fibroblasts but grew in a lacy pattern and never became confluent. 15 AF control lines had transferase activity of 10.1 - 34.9 by consumption assay. There was no correlation with cell type (epithelioid vs. fibroblast) or with state of confluency. Prenatal diagnosis for galactosemia may be falsely interpreted if the UDPG consumption assay is used and the fetus is heterozygous for galactosemia.