Acute hemolytic transfusion reaction caused by anti-M antibodies: a case report and literature review.

Objective: We report a rare case of acute hemolytic reactions caused by immunoglobulin (Ig)M anti-M antibody and present a literature review.

Case report: A 61-year-old male patient who underwent blood transfusion developed fever, chills, soy sauce-colored urine, and changes in laboratory test results, including persistently decreased hemoglobin levels, neutrophilia, elevated lactate dehydrogenase level, acute kidney injury, mild acute liver injury, and activation of the coagulation system, indicating acute hemolytic transfusion reaction (AHTR). Antibody screening and major crossmatching results indicated weak positive at 37°C for both posttransfusion and pretransfusion sample. Subsequent serological examinations indicated the presence of IgM anti-M antibodies in plasma but the direct antiglobulin and elution tests were negative. Antibody hemolytic activity assay confirmed AHTR caused by anti-M. The transfused red blood cells were MM and the patient is NN. These signs and symptoms disappeared rapidly and required no additional interventions before discharge.

Conclusion: The accurate diagnosis of anti-M antibody-mediated acute hemolysis is essential for guiding treatment decisions.