Multiple myeloma is a plasma cell malignancy characterized by clonal proliferation of plasma cells in the bone marrow and associated organ damage. Usually, patients with myeloma present with a single monoclonal protein in serum and/or urine constituted by one heavy chain and one light chain. In less than 5% of the patients, more than one monoclonal protein can be identified. The aim of our retrospective multicenter matched case-control study was to describe the characteristics of cases with biclonal myeloma and compare them against a control group of monoclonal myeloma patients matched by age, sex, and year of diagnosis. A total of 50 previously untreated cases with biclonal myeloma and 50 matched controls with monoclonal myeloma were included in this study. The controls were matched (1:1) for age, sex, year of diagnosis, and participating center. There were no differences in the rates of anemia (52 vs. 59%; p = 0.52), renal dysfunction (36 vs. 34%; p = 0.83), hypercalcemia (9 vs. 16%; p = 0.28), or presence of lytic lesions (23 vs. 16%; p = 0.38) between groups. Similarly, there was no difference in the rates of overall response to therapy (85 vs. 90%; p = 0.88) or survival rates of cases with biclonal myeloma and controls with monoclonal myeloma (4-year survival 72 vs. 76%; p = 0.23). Results of our study suggest that patients with biclonal myeloma have similar response and survival rates than patients with monoclonal myeloma.

Monoclonal gammopathy of unknown significance (MGUS) is a benign condition that carries a risk of progression to haematological malignancy. It is accepted that MGUS should not be treated until progression to multiple myeloma or another lymphoid malignancy. Recently, growing evidence has started to show that even small monoclonal clones can be responsible for renal impairment. Long-term observation of patients with monoclonal gammopathy and abnormal renal function showed that this condition can significantly affect renal and overall survival. Patients with monoclonal gammopathy with renal impairment have also higher risk of relapse after kidney transplantation. Among patients with monoclonal gammopathy of unknown significance there is a group of defined monoclonal component-related diseases, which includes:light-chain amyloidosis, monoclonal immunoglobulin deposition disease, crystal-storing histiocytosis, cryoglobulinaemias, and some others. They can be diagnosed on the base of clinical features and on histological examination. In patients with monoclonal protein and deposition of fragments or whole particle of monoclonal immunoglobulin with distinct localisation and substructural organisation can be found.The treatment strategy is targeting of B cell clones, which requires administration of chemotherapeutics or other medications that are used for the treatment of lymphoid malignancy or myeloma. The choice of therapeutic agent should take into account the current kidney status. Treatment of renal disease should not differ from other patients with similar conditions not related to monoclonal protein. The expert opinion is that the presence of monoclonal gammapathy is not a contraindication to kidney transplantation.