Fatal cerebral hemorrhage in a patient with CD19-positive IgM-producing aggressive plasma cell myeloma, hyperviscosity syndrome and cryoglobulinemia.

IgM plasma cell myeloma (PCM) is a rare entity, and CD19 positivity is found in only 1-4% of PCM. Here we report a unique case of IgM PCM, in which the plasma cells are positive for CD19. Clinically, the patient presented with hyperviscosity syndrome, mimicking the clinical manifestation of Waldenstrom's macroglobulinemia. In addition, the IgM para-protein from the patient behaved like cryoglobulins, which interfered with some of the laboratory measurements and resulted in erroneous platelet count, mean platelet volume, and serum IgM level. Despite chemotherapy, the PCM persisted and progressed to plasma cell leukemia, and the patient died of a left frontal hematoma with widespread cerebral hemorrhage extending from left lateral ventricle, third ventricle, fourth ventricle, to cisterna magna. This case represents the first CD19+ IgM-producing PCM and the second case of brain hemorrhage due to plasma cell myeloma/leukemia.