IgM Multiple Myeloma: A Rare Subtype Highly Sensitive to Lenalidomide

Background: IgM multiple myeloma (MM) are very rare plasmaproliferative disorders representing 0.5–1.2% of all cases of MM and < 0.2% of all IgM monoclonal gammopathies. Clinical criterion are not always helpful in differentiating IgM MM from Waldenstrom macroglobulinemia. However, the presence of lytic bone lesions, absence of lymphadenopathy and/or hepatosplenomegaly, presence of translocation of the immunoglobulin heavy chain locus at 14q32 [t(11;14), t(14;16), t(4;14)], and strong expression of CD138 by the plasma cells are useful in the diagnosis of IgM MM. It has been our experience and of others that these cases have an aggressive behavior at presentation, shorter survival than IgG and IgA MM and poor response to therapy for lymphoplasmacytoid lymphomas. We present here 2 cases of IgM MM with a dramatic response to Lenalidomide and low dose dexamethasone (Rev/Dex)

Results: Baseline patient characteristics at time of diagnosis of IgM MM and therapy outcome are presented in the following 2 tables:

Table 1.

Table 2. Best Response to therapy

Conclusions: This is the first report that we are aware of a rapid and dramatic response to lenalidomide and low dose dexamethasone in these rare cases of IgM MM with poor response to NHL-type treatment. Lenalidomide-based therapy might abrogate poor prognosis cytogenetics in this unusual subtype of MM (case #2), however, follow up for this patient is still very short.