Multiple myeloma (pathogenesis, clinical features, diagnosis, differential diagnosis). Part I

Multiple myeloma (MM) is a malignancy characterized by bone marrow infiltration with plasma cell and extensive skeletal bone destruction resulting in bone pain and fractures. This review presents typical laboratory findings and clinical presentation of multiple myeloma. Multiple myeloma is definite when the following hallmarks are present: ³ 10% of clonal plasma cells in the bone marrow, M protein in serum or urine (except nonsecretory myeloma), hypercalcemia, renal insufficiency, anemia, or osteolytic lesions in skeletal bones. Monoclonal (M) proteins are detected using serum protein electrophoresis and immunofixation. In addition, urine protein electrophoresis and immunofixation or a serum free light-chain assay are essential. The International Staging System classifies MM patients into three groups of risk — standard, intermediate, or high — depending on the b2-microglobulin and albumin serum levels. The presence of any one of the following indicates high-risk myeloma: a 13q deletion or hypodiploidy on metaphase cytogenetic studies, a 17p deletion, immunoglobulin heavy-chain translocations t(4;14) or t(14;16), or a plasma cell labeling index ³ 3%. This review presents laboratory findings and clinical manifestations of monoclonal gammopathy of undetermined significance, asymptomatic myeloma (‘smouldering myeloma’), nonsecretory myeloma, solitary bone plasmacytoma, extramedullary plasmacytoma, plasma cell leukemia, Waldenstrom’s macroglobulinemia, amyloidosis, and other diseases.