Moderate hemolytic disease of the newborn due to anti-Hr₀ in a mother with the D––/D–– phenotype

Hemolytic disease of the newborn (HDN) due to anti-Hr₀ antibody is typically severe and often fatal. We report a case of moderate HDN due to anti-Hr₀ in a woman with the D––/D–– phenotype. A 33-year-old woman delivered her second child who was mildly jaundiced. The highest level of bilirubin was 26.1 mg/dL on the third day postpartum and the hemoglobin concentration was 14.0 g/dL. The newborn recovered after phototherapy and no mental retardation was noticed after 1 year of follow up. An exchange transfusion was excluded due to the lack of a compatible donor and the physical condition of the mother precluded blood donation. The maternal RBCs were D+C–c–E–e–; only G and Rh29 of the Rh system were expressed. Thus, her probable phenotype was D––/D––. Her alloantibody was identified as anti-Hr₀ (anti-Rh17) as it reacted with all red blood cells (RBCs) but not her own, other D-– RBCs, and Rh_null RBCs. The results of the antibody titer (64) and activity in a chemiluminescense test (CLT; 34%) were consistent with a moderate HDN. Family studies were negative for the D––/D–– phenotype and consanguinity was not proved. This is the first described case of moderate HDN due to anti-Hr₀. The result of antibody activity in the CLT might be helpful in predicting the severity of HDN in other rare HDN cases. Immunohematology 2000;16:109–111.