Clinical characteristics and outcome of immunoglobulin M-related disorders.

We analyzed the clinical features and prognostic factors for transformation of immunoglobulin Mrelated disorders (IgM-RDs) to malignant lymphoproliferative disease (MLD) in 83 patients with IgM-RDs. We studied 19 patients with type I cryoglobulinemias, 56 patients with type II cryoglobulinemias, 5 patients with peripheral neuropathies (PNs), and 3 patients with idiopathic thrombocytopenic purpuras. Fourteen patients with cryoglobulinemias presented with mild to moderate hepatomegaly with or without splenomegaly. Fourteen patients with type II cryoglobulinemias had arthralgias and/or vascular purpura (12 receiving corticosteroids), and 7 presented with PN. These latter patients and those with PNs without cryoglobulinemia were treated with steroids, cyclophosphamide, or polychemotherapy with/without plasma-exchange. Cumulative probability of evolution to MLD at 5 years was 15% (95% CI; 5%-25%). At a median of 62 months (12-195 months), 8 cases of IgM-RDs (8.4%) evolved to overt Waldenstrom's macroglobulinemia (n = 6), 1 case to non-Hodgkin's lymphoma, and 1 case to B-cell chronic lymphocytic leukemia. At univariate analysis, male sex (P = 0.02), IgM level > or = 3 g/dL (P < 0.0001), detectable Bence Jones proteinuria (P = 0.0005), lymphocytosis (P = 0.049), and high erythrocyte sedimentation rate (P = 0.003) significantly correlated with the evolution risk. Age, blood cell counts, b2-microglobulin level, degree of marrow lymphoplasmacytic infiltration, type of cryoglobulinemia, and hepatitis C virus positivity did not correlate with transformation. Although IgM-RDs represent a distinct clinical entity frequently requiring treatment in view of the IgM-related symptoms, their evolution probability and prognostic factors for malignant transformation seem to widely overlap those described for asymptomatic IgM monoclonal gammopathies.