Delayed Hemolytic Transfusion Reaction With Hyperhemolysis Syndrome Due to Anti-M Alloantibody in Myelofibrosis: A Case Report.

Hyperhemolysis syndrome (HHS) and delayed hemolytic transfusion reaction (DHTR) commonly occur in patients with sickle cell disease (SCD) and thalassemia, due to the need for recurrent red blood cell (RBC) transfusion, but rarely in patients with myelofibrosis. HHS is a life-threatening condition that occurs with or without DHTR, in which both transfused and autologous RBCs are destroyed. It needs a high clinical suspicion for diagnosis, especially when there is a drop in hemoglobin level to the level of pretransfusion of RBCs, accompanied by hyperbilirubinemia and reticulocytopenia.