Three cases of multiple myeloma in which the preclinical asymptomatic phases persisted throughout 15 to 24 years.

During the period from 1950 to 1952, three patients were studied by electrophoresis according to Tiselius on account of anticomplementary activity at WR; the presence of an M-component was demonstrated. On several later occasions it was observed that this component at first seemed to remain unchanged, later it was slightly increased; repeated examinations did not give evidence of multiple myeloma. At intervals ranging from 15 to 24 years after the primary demonstration of the M-component, all three patients presented with symptoms of multiple myeloma and died within less than one year after the disease had been diagnosed. The following conclusions are drawn:(1) The preclinical phase of multiple myeloma may cover up to 24 years.(2) A presence of multiple myeloma cannot be precluded, even after follow-up throughout 24 years, in cases of the so-called "benign monoclonal gammopathy".