[Benign monoclonal gammopathy].

Monoclonal gammopathy of undetermined significance (MGUS) denotes the presence of a monoclonal protein (M protein) in patients, without evidence of multiple myeloma, macroglobulinemia, amyloidosis or other related diseases. Differential diagnosis of MGUS from multiple myeloma is difficult in cases of the unusual type of each disease. A serum monoclonal protein concentration of less than 3 g/dl, normal polyclonal immunoglobulin, no or small amount of Bence Jones proteinuria and the infiltration of plasma cells of less than 10% in bone marrow are suggestive of MGUS. In the literature, about 25% of the MGUS have developed multiple myeloma or related diseases in a long term follow-up. This fact calls our attention to the management of MGUS.