Multiple Myeloma is best described as

• A. A malignant disease characterized by the overgrowth of abnormal plasma cells in the bone marrow
• B. A benign tumor of the bone
• C. A viral infection
• D. A disorder of red blood cells

Answer: (A)

Multiple myeloma is a malignant plasma cell neoplasm arising in the bone marrow. Plasma cells are antibody-secreting cells derived from B lymphocytes; in this disease a single clone of these cells becomes cancerous and expands, crowding out normal marrow elements. This clonal overgrowth explains both the blood abnormalities (anemia and infection risk from reduced normal hematopoiesis) and the presence of a monoclonal immunoglobulin (M protein) in blood or urine, which can damage kidneys and affect immune function. The malignant plasma cells also promote bone destruction by activating osteoclasts, leading to osteolytic lesions and bone pain. In short, it is a malignant disease characterized by abnormal, clonal plasma cells in the bone marrow—not a benign bone tumor, not a viral infection, and not primarily a red blood cell disorder.