A case of anti-Rd causing fetal anemia.

BACKGROUND: Rd (SC4) is a low-frequency antigen of the Scianna blood group system. Only very few reports on anti-Rd in pregnancy exist. Mild to moderate hemolytic disease of the newborn caused by anti-Rd has been reported. This report may add further information on the clinical significance of anti-Rd for the fetus.

CASE REPORT: In a case of severe fetal anemia (hemoglobin concentration, 3.0 g/dL) repeated intrauterine transfusions were required. The strongly positive direct antiglobulin test (DAT) of the fetal red blood cells led to the diagnosis of hemolytic disease. The routine antibody screen was negative, extended testing revealed a maternal anti-Rd with a titer of 256. Both the newborn and her father were confirmed to carry the SC*01.04 allele.

CONCLUSION: Anti-Rd can cause fetal anemia. Low-frequency antigens including Rd are normally not present on screening cells. Antibodies directed against low-frequency antigens will usually not be detected by routine antibody screening in pregnancy. Thus, in cases of fetal anemia the DAT should always be included in the diagnostic workup.