Anti-D alloimmunization by Asia type DEL red blood cell units in a D-negative Thai patient

Background DEL phenotype is a rare Rh variant that cannot be detected by routine serological typing, and DEL individuals are thus typed D-negative (D–). Anti-D alloimmunization has been reported in “true” D– patients receiving DEL red blood cells (RBCs). Case presentation A 17-year-old, D– Thai male patient suffering from immunodeficiency syndrome with negative antibody screening received RBC units from 17 serological D– donors over a period of seven months due to acute respiratory failure with anemia. Before the 12th transfusion, anti-D production was detected. He was later transfused with RBCs from six other apparent D– donors. In order to elucidate anti-D production, all 17 blood donors were investigated by replicative serological testing and molecular analysis to identify potential RHD gene variants. All donors were confirmed D– by routine method, but as many as 12/17 were positive by adsorption-elution testing. Molecular analysis showed that five donors, including four whose blood was transfused before anti-D production occurred, carry the Asia type DEL allele, and are thus predicted to express a DEL phenotype. These data clearly suggest that 1/ the alloimmunized D– patient was exposed to D antigen, 2/ our adsorption-elution test is currently defective to identify DEL RBCs, and 3/ molecular analysis is highly valuable for Asia type DEL allele screening. Conclusion For the first time in Thailand, we report anti-D alloimmunization in a serological D– patient transfused by Asia type DEL RBC units. This work definitely supports the implementation of a dedicated policy for DEL blood management including molecular testing.