A case of anti-Rh17 (anti-Hro) antibody in D··phenotype, a rare alloimmunization complicating transfusion management.

Rh blood group system is highly immunogenic, encoded by two closely linked genes; RHD and RHCE. The proximity of the genes can result in mutations resulting in hybrid genes and hence Rh variants like D-- and D··. Both variants are similar, difficult to distinguish serologically. D·· is characterized by RH CE-D-CE rearrangement resulting in Evans antigen. Anti-Rh17/Hro formed as a result of alloimmunization can cause Haemolytic Disease of Foetus as well as hemolytic transfusion reactions. We report a case of 60- year-old female surgical patient, alloimmunized as a result of previous transfusion. The resultant antibody antiRh17 to high incidence antigen led to incompatible crossmatches. The patient was managed conservatively without transfusions. Subsequent analysis confirmed D·· phenotype with RH CE-D-CE rearrangement, Evans antigen positive. This article emphasizes the importance of extended typing of patients prior to transfusion and highlights the importance of establishing rare donor registries and frozen blood inventories in case of antibodies to high frequency antigens.