[Clonal immunoglobulin rearrangement in patients with essential cryoglobulinemia].

'Essential' cryoglobulinemias (EC) are characterized by the precipitation of immunoglobulins (Igs) from the sera of patients at temperatures below 25 degrees C. The cryoprecipitate of type I EC patients is comprised of a monoclonal Ig while that of patients with type II or 'mixed' EC contains monoclonal auto-antibodies with rheumatoid factor activity. In order to define if the high cryoglobulin production rate is related to a clonal B-cell expansion the rearrangement of Ig genes was investigated by Southern blot analysis of DNA extracted from peripheral blood lymphocytes of EC patients. Clonal expansion of B cells could be detected using Ig light and heavy chain specific DNA probes in 3/4 patients with type I EC and 4/12 patients with type II EC. In the group of patients with clonal Ig gene rearrangements, in two cases with type I EC and one case with type II EC, alterations of the c-myc locus was also noted. Demonstration of clonal B-cell expansions in EC patients shows that the clonal type of Ig gene rearrangements is not a unique marker of malignant lymphomas. Since malignant B-cell lymphomas can develop in a small number of EC cases, the follow-up of these patients should be pursued indefinitely.