Anaphylactic Transfusion Reaction to Washed Packed Red Blood Cells (pRBCs)

The annual blood transfusions in the United States exceed 16 million units, and 1% of the cases experience adverse events. Febrile nonhemolytic transfusion reaction is most common accounting for 1%–3% of the cases. Anaphylactic transfusion reaction accounts for 0.00002% of the units transfused. Washed packed red blood cells (pRBCs) are typically used to mitigate anaphylactic risk in immunoglobulin A (IgA)–deficient recipients when IgA‐deficient donor RBCs are unavailable. We present two extremely rare cases with anaphylaxis to washed pRBCs. This challenges the assumption that washing alone prevents IgA‐mediated anaphylaxis and expands the differential for transfusion reactions in IgA‐sufficient individuals. The cases add to the literature by demonstrating that severe reactions can occur despite IgA sufficiency and multiple pretreatment measures, underscoring the need for vigilance and exploration of alternative transfusion strategies.