[Monoclonal gammopathies of undetermined significance called "MGUS"].

While the discovery of a monoclonal gammopathy in the blood of a patient sometimes leads to the diagnosis of multiple myeloma, immunocytoma or other B-cell lymphoproliferative syndromes, "secondary" monoclonal dysproteinemia is seldom considered. In most cases "monoclonal gammopathy of undetermined significance" (MGUS) is diagnosed. After ten years about 25% of these cases evolve to true multiple myeloma or Waldenström's disease. Other MGUS usually remain asymptomatic, though sometimes a complication such as amyloidosis or cryoglobulinemia may occur as a result of the "perverse" effect of the monoclonal protein. Some cases are described.