Definition of Multiple Myeloma

Multiple myeloma is a hematologic (blood) cancer that develops in the bone marrow. Myeloma is a cancer of the plasma cells, which are one of the many types of blood cells that arise from the stem cells in bone marrow. Plasma cells are responsible for producing antibodies (immunoglobulins) which are critical for maintaining the body’s immune system. Multiple Myeloma typically occurs in bone marrow with the most activity, which is the marrow in the spine, pelvic bones, ribs, and area of the shoulders and hips.

In multiple myeloma, normal plasma cells transform into malignant myeloma cells and produce large quantities of an abnormal immunoglobulin called monoclonal protein, or M Protein. Unlike normal immunoglobulin, M protein does not benefit the body. Instead, the abnormal cells crowd out and inhibit the production of normal blood cells and antibodies in the bone marrow. In addition, groups of myeloma cells cause other cells in the bone marrow to remove the solid part of the bone and cause soft spots in the bone. These soft spots are called osteolytic lesions. Bone lesions, along with other signs of bone loss are common, although they do not occur in all individuals with myeloma.