Monoclonal Gammopathy—a Diagnostic Challenge

Four patients with IgG multiple myeloma (MM) and an unusually indolent course are presented. They had received no cytostatic therapy for 12–23 years. The M-component was initially 25–33 g/l, the bone marrow plasma cell percentage was 4–6%, but bone lesions were not demonstrated. A marked increase in size of the M-component and in the plasma cell percentage was noted in all patients, but a definitely neoplastic proliferation in only one patient. Spontaneous regression of the M-component was observed in two patients. In the light of the present cases we believe that neither a high level of the M-component nor an increase in its size should be used alone as indicators of a malignant course in MM patients. An indolent, non-progressive variant obviously occurs as one extreme in the clinical spectrum of this disorder with a course sometimes extended over 10–20 years.