Type II mixed cryoglobulinemia (MC) is a systemic vasculitis characterized by the presence in the serum of a monoclonal cryoprecipitable IgM with rheumatoid factor (RF) activity. Hepatitis C virus (HCV) has been recognized as its major etiologic factor. Because MC frequently evolves into overt B-cell non-Hodgkin's lymphoma (NHL), chronic HCV infection is hypothesized to lead to both benign and malignant lymphoproliferative disease. In this study, we investigated mutations in the V(H) and V(K) genes of the B-cell clone originating the overt B-cell lymphoma in a subject with MC. Mutational patterns were analyzed longitudinally in two bone marrow biopsies obtained at the stage of MC, as well as in multiple involved tissues (bone marrow, liver, and peripheral blood cells) at the stage of overt NHL. Hybridization of variable-diversity-joining (VDJ) PCR products with a probe specific for the neoplastic clone indicated that the lymphoma originated from one of the clones over-stimulated during MC. This clone producing an IgM highly homologous to a protein with RF specificity may explain the MC syndrome in the patient. Moreover, the presence of an IgH ongoing mutation process and the expression of an Ig antigen receptor significantly homologous to an anti-HCV protein support the hypothesis that the MC syndrome and the subsequent evolution to NHL are antigen-driven lymphoproliferative processes possibly sustained by HCV. Furthermore, the marked reduction in intra-clonal diversity in the last bone marrow biopsy obtained at the stage of overt NHL points out a minor dependence of the cells on the antigen-driven mechanism, although an intrinsic propensity of the neoplastic cell to undergo replacement mutations cannot be excluded.
Copyright 2000 Wiley-Liss, Inc.