RESUMO
INTRODUCTION: Anti-M antibodies are usually inactive at physiologic temperatures (37 °C). Rarely, these antibodies have been reported to react at physiologic temperatures, resulting in clinically significant hemolytic transfusion reactions or hemolytic disease of the fetus and newborn. PATIENT AND METHODS: We describe a case of an acute hemolytic transfusion reaction due to an anti-M alloantibody reacting at physiologic temperatures in a critically ill patient. RESULTS: Proper identification and management of anti-M antibody-mediated acute hemolysis rapidly improved and stabilized her hemoglobin. CONCLUSION: Differentiation between anti-M antibody-mediated acute hemolysis and its differential diagnoses is of critical importance to guide therapeutic decisions in these rare clinical scenarios.
