IgA plasma cell myeloma presenting as cold agglutinin-induced haemolytic transfusion reaction.

Cold agglutinins produced in the setting of B cell neoplasms, such as lymphoplasmacytic lymphoma and plasma cell myeloma, can mediate autoimmune haemolytic anemia. Transfusion of these patients can exacerbate cold agglutinin-mediated haemolysis. Moreover, the workup for these reactions represents a diagnostic challenge due in part to false negative direct antiglobulin tests (DATs). Here, we report an anaemic patient who after a red blood cell (RBC) transfusion performed without blood warming, experienced a DAT-negative haemolytic transfusion reaction, and was later diagnosed with IgA-multiple myeloma, which showed an uncommon granular pattern by CD138 immunohistochemistry. Extensive workup excluded other diagnostic possibilities, including the presence of Donath-Landsteiner antibodies and cryoglobulins. Successful treatment with CyBorD (cyclophosphamide, bortezomib and dexamethasone) achieved complete remission, and additional RBC transfusions using warmers were completed uneventfully.