Multiple myeloma (MM), a plasma cell dyscrasia, is the most common primary malignancy of the bone marrow.The etiology of myeloma is largely unknown, although genetic predisposition and environmental factors have been speculated. MM arises from malignant plasma cells that clonally expand and accumulate in the bone marrow. These clonal plasma cells produce high levels of monoclonal immunoglobulins. Plasma cell dyscrasias are classified as monoclonal gammopathy of undetermined significance, solitary plasmacytoma, smoldering myeloma, active myeloma, extra-skeletal myeloma, or plasma cell leukemia.