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.