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BACKGROUND: AnWj is a high-prevalence red blood cell (RBC) antigen in the ISBT 901 series. Only nine reports of anti-AnWj have been published since it was first documented in 1972; two of these cases involved transfusion reactions. We present a case of a patient with aplastic anemia who developed anti-AnWj with clinically significant hemolysis after transfusion of AnWj-positive RBCs.

STUDY DESIGN AND METHODS: A 56-year-old woman with aplastic anemia developed a pan-reactive antibody with clinically significant hemolysis after transfusion of RBCs. Investigations included antibody identification by serologic methods at the national immunohematology reference laboratory and the in vitro monocyte-monolayer assay (MMA) to predict clinical significance.

RESULTS: The antibody was identified as having specificity for the AnWj antigen. The posttransfusion MMA indicated that the antibody had complement-fixing capability highly likely to cause clinically significant acute hemolytic transfusion reactions. The patient required long-term transfusion support with AnWj-negative RBCs and Lu(a−b−) RBCs of the In(Lu) type which have reduced AnWj expression. Cross-Canada and international collaboration was required to obtain rare units for transfusion.

CONCLUSION: A case of acute hemolytic transfusion reaction caused by anti-AnWj is reported in a patient with aplastic anemia requiring allogeneic stem cell transplantation. This is the second documented case of anti-AnWj to cause a hemolytic transfusion reaction. The case demonstrates the complexity of managing patients with rare antibodies and the importance of international collaboration in the management of these difficult cases.