RESUMEN
Multiple myeloma is a clonal proliferation of the plasma cell line that accounts for approximately 10% of all hematological malignancies. It is characterized by abnormal growth of plasma cells producing monoclonal immunoglobulin or light chain (paraprotein), with subsequent development of osteolytic bone lesions, anemia, hypercalcemia, and renal failure. In 3-6% of myeloma patients, more than one monoclonal protein (usually two) is discovered, with different heavy or light chain or both. These additional monoclonal proteins may be identified at the time of diagnosis or appear later during an observation or therapy. The authors describe two patients with biclonal myeloma, one diagnosed during evaluation for newly discovered renal failure, and one identified in the course of treatment of monoclonal gammopathy. The discussion of the diagnosis, natural history, and prognosis in patients with biclonal myeloma are also reported.