A cold scare: Formation of cold reactive anti-A1 coinciding with gross hemolysis

Here, we report a rare case of a cold-reactive anti-A1 alloantibody (after multiple transfusions with group A1 RBC units) in a 76 year old male patient (A2) with history of myelodysplastic syndrome and metastatic carcinoma who presented with hemolytic anemia and dark urine. The patient had previously typed as blood type A without reverse typing reaction for anti-A1; as a result, the patient had been transfused with group A1 RBCs. Four days prior to discovery of the ABO discrepancy, the patient had a febrile transfusion reaction associated with his A1 RBC transfusion. On admission, his immunohematology workup demonstrated an alloantibody to anti-A1 that coincidentally appeared during a new onset of hemolytic anemia. Case reports of patients with hemolytic anemia with a newly developed anti-A1 alloantibody are sparse in the literature, and this case is particularly interesting as the cold reactive anti-A1 (without demonstrable wide thermal amplitude) appeared to form after alloimmunization and in the setting of an underlying malignancy.