'Benign' monoclonal gammopathy. A misnomer?

A series of 241 patients with monoclonal protein but no evidence of multiple myeloma, macroglobulinemia, amyloidosis, or lymphoma (benign monoclonal gammopathy) were followed up for more than ten years. The patients were classified as follows: group 1, patients without increase of monoclonal serum protein during follow-up (benign) (37%); group 2, patients with greater than 50% increase of monoclonal protein or development of monoclonal urine protein (5%); group 3, patients who died of unrelated causes (39%); and group 4, patients in whom myeloma, macroglobulinemia, amyloidosis, or related diseases developed (19%). The median interval from recognition of the monoclonal protein to diagnosis of multiple myeloma was 98 months; macroglobulinemia, 115 months; and systemic amyloidosis, 92 months. No laboratory or clinical data initially differentiated patients with benign gammopathy from those in whom serious diseases developed. Consequently, serial measurement of serum monoclonal protein is essential.