[Nosology and management of monoclonal gammapathy].

Monoclonal gammapathy (MG) affects about 1% of the general population, and its prevalence is higher in elderly subjects. Monoclonal gammapathy of undetermined significance (MGUS), the most common disorder, is asymptomatic and associated with normal hemoglobin, calcium and creatinine levels and a monoclonal component of less than 15 g/l. A B cell neoplasm should be suspected in patients with clinical manifestations and/or abnormal hemoglobin, calcium or creatinine levels, and/or a monoclonal component >15 g/l. Multiple myeloma tends to be associated with IgG or IgA MG, and Waldenstrom's macroglobulinemia with IgM MG Patients with MGUS do not need treatment but only yearly follow-up (symptoms, protein electrophoresis, hemoglobin, calcium and creatinine assay), as the estimated annual risk of malignant transformation is about 1 %. Factors predictive of malignant transformation include the type of serum monoclonal protein, the monoclonal protein concentration, bone marrow plasmocytosis, and the serum free light chain ratio.