Double gammopathies: incidence and clinical course of 20 patients.

The presence of 2 M-components in single patients (double gammopathy) was studied retrospectively by means of the electrophoresis files in Umeå (serving a population of approximately 150 000 inhabitants). During the 11-year period 1974-1984, 109 000 electrophoreses were performed, among which 1034 patients with gammopathy were found. Of these, 20 (2%) had double gammopathy; 3 were associated with lymphoma, 7 with myelomatosis, 9 with monoclonal gammopathy of undetermined significance (MGUS), and 1 with lupus erythematosus disseminatus. It is suggested that one subgroup of double gammopathy (6 patients) had a neoplastic cell clone combined with a normally regulated cell line, the latter marked by a transient M-component. Another subgroup (14 patients) seems to have 2 coexisting different neoplastic cell lines, with persistent double gammopathy.