A fatal case of acute hemolytic transfusion reaction caused by anti-Wr^a: case report and review of the literature

The red blood cell (RBC) antigen Wr^a is a low-prevalence antigen first described in 1953 by Holman and assigned to the Diego system in 1995. Because of its low prevalence, Wr^a is usually absent on commercial screening RBCs and antibody identification panels. When Wr(a+) screening RBCs are available, the corresponding antibody, anti-Wr^a, is often found in sera from healthy individuals, patients, and pregnant women. Anti-Wr^a can cause both hemolytic transfusion reactions and hemolytic disease of the fetus and newborn. We describe a fatal acute hemolytic transfusion reaction caused by anti-Wr^a in a patient with no other RBC alloantibodies. Serologic investigation showed that one of the RBC units the patient received was Wr(a+). Immunohematology 2021;37:20–24.