The monoclonal gammopathies, also referred to as paraproteinaemias, are a group of neoplastic (or potentially neoplastic) diseases associated with the proliferation of a single clone of immunoglobulin-secreting plasma cells. Monoclonal gammopathy of undetermined significance (MGUS) is an asymptomatic clonal plasma cell disorder characterized by a serum monoclonal (M)-protein level less than 30 g/litre, less than 10% of monoclonal bone marrow plasma cells, and no evidence of hypercalcaemia, renal insufficiency, anaemia, or bone lesions related to the plasma cell proliferative process, and no evidence of any other myeloma-defining events. Observation is the standard of care. Plasma cell myeloma is a clonal plasma cell malignancy that accounts for about 10% of haematological cancers. The cause is unknown. Fluorescence in situ hybridization of bone marrow plasma cells reveals specific primary translocations or trisomies in more than 90% of patients. The presence of del 17p, t(4;14), t(14;16), and t(14;20) occur in 20 to 25% of patients, and indicate higher-risk disease. Waldenström’s macroglobulinaemia (WM) is characterized by the presence of an IgM M-protein, 10% or more lymphoplasmacytic infiltration of the bone marrow, and symptoms such as anaemia, lymphadenopathy, and hyperviscosity. Rituximab, a monoclonal antibody directed against CD20, is used as initial therapy in conjunction with other active drugs. Ibrutinib is a new agent that is highly active against WM. The median survival is longer than 5 years. Immunoglobulin light-chain amyloidosis is a clonal plasma cell disorder characterized by tissue deposition of fibrils consisting of monoclonal κ or λ light chains. Standard treatment is with bortezomib, cyclophosphamide, dexamethasone, and autologous stem cell transplantation in selected patients.
2021 European Myeloma Network review and consensus statement on smoldering multiple myeloma: how to distinguish (and manage) Dr. Jekyll and Mr. Hyde
