Immunoglobulin M (IgM) multiple myeloma versus Waldenström macroglobulinemia: diagnostic challenges and therapeutic options: two case reports

In this report, we describe two cases of immunoglobulin M neoplasm with the same histological bone marrow presentation but with different clinical behavior, cytogenetics, and biological assessment. On the basis of comprehensive diagnostic workup, these patients were considered to have different diseases and treated accordingly with different approaches. Patient 1 (Caucasian man) presented with increased serum protein and immunoglobulin M (7665 mg/L) with an M-spike electrophoresis of 4600 mg/L. His bone marrow biopsy revealed a small-cell immunoglobulin M multiple myeloma. The result of testing for the MYD88 L265P mutation was negative, while fluorescence in situ hybridization analysis showed translocation t(11,14). A diagnosis of immunoglobulin M-κ multiple myeloma was made. Patient 1 was a candidate for bortezomib plus thalidomide and dexamethasone, followed by autologous stem cell transplant consolidation. Patient 2 (Caucasian man) showed an M-spike by protein electrophoresis (300 mg/L, 4.9%), with serum immunoglobulin M level of 327 mg/L. His bone marrow biopsy revealed immunoglobulin M-κ multiple myeloma. Computed tomography showed many enlarged lymph nodes and splenomegaly. Patient 2’s clinical features were suggestive of Waldenström macroglobulinemia, in contrast to the bone marrow biopsy results. The result of testing for the MYD88 L265P mutation was positive. Patient 2 was diagnosed with Waldenström macroglobulinemia and received rituximab, cyclophosphamide, and dexamethasone.