OBJECTIVETo improve the understanding of the clinical and laboratory features of the IgM multiple myeloma (MM).

METHODSThe clinical data of four cases of IgM MM patients were collected, their clinical and laboratory features were summarized and analyzed.

RESULTSFour patients met the criteria of IgM MM. They were all male. The age at the diagnosis ranged from 54 to 69 years. The primary symptoms included bone pain, hyperviscosity and bleeding. Three cases had κ-chain and only one case had λ-chain. They were all staged ⅢA according to the Durie-Salmon staging system (DSS). One case stagedⅠand three cases staged Ⅱ according to the international staging system (ISS). The average value of IgM, hemoglobin, serum calcium, creatinine and the proportion of bone marrow plasma cells were 83.6 (52.9-111.0) g/L, 79.5 (61.0-105.0) g/L, 3.20(2.11-6.00) mmol/L, 104.3 (56.0-171.0) μmol/L and 0.558 (0.290-0.775), respectively. Bone destruction was found in 3 cases. Immunophenotypes of bone marrow plasma cells were analyzed in 3 patients. Results showed that these cells expressed CD38 and CD138, and did not express CD19, CD20 and CD117. Chromosome and fluorescence in situ hybridization (FISH) analysis were carried out in 4 cases and found that all of them had IgH translocations and 1q21 amplification, 2 cases had 13q and 17p deletion, and 3 cases had t(11;14). Three patients received bortezomib-based regimens as induction therapy and reached partial response (PR) - very good partial response (VGPR). Followed up to November 30, 2012, the median progress-free survival (PFS) and overall survival (OS) of the 4 cases were only 6.0 (2.5-7.0) months and 17.5 (2.5-27.0) months, respectively.

CONCLUSIONSIgM MM is very rare and is no more than 0.5% in all types of MM. IgM MM have frequent t(11;14) and amp(1q21). Bortezomib-based regimens are effective for it, however, the disease progresses rapidly and has poor prognosis.