Hemolysis due to anti-IH in a patient with beta-thalassemia and Mycoplasma pneumoniae infection

Anti-IH is a common cold agglutinin that is typically clinically insignificant. We present a case that resulted in hemolysis. A 32-year-old male patient with transfusion-independent beta-thalassemia intermedia presented with symptomatic anemia. His blood sample typed as group B, D+ and demonstrated multiple alloantibodies and cold autoantibodies. He was transfused uneventfully, but re-presented 10 days later with recurrent, worsening anemia. At this time, transfusion of group O, phenotype-matched red blood cells (RBCs) resulted in an acute hemolytic reaction. While anemia was initially attributed to drug-mediated bone marrow toxicit y and subsequently to a delayed hemolytic reaction, further evaluation revealed Mycoplasma pneumoniae infection and a cold agglutinin (anti-IH specificity), indicating a likely autoimmune-mediated anemia due to an infectious etiology. Subsequent transfusion of 2 group B, phenotype-matched RBC units using a blood warmer was uneventful. Anti-IH is only rarely associated with hemolytic transfusion reactions, which may be exacerbated when transfusing group O RBC units to group B patients. M. pneumoniae infection likely led to cold agglutinin–mediated hemolysis of endogenous and transfused RBCs. The patient was successfully managed with intravenous immunoglobulin, steroids, rituximab, erythropoietin, hydroxyurea, and amoxicillin clavulanate/azithromycin. This case illustrates the importance of infectious disease evaluation in patients with unexplained anemia, the potential clinical significance of autoanti-IH, and the value of providing type-specific RBC units in these circumstances.