Definition of Multiple Myeloma

Multiple myeloma is a hematologic (blood) cancer that develops in the bone marrow, 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. Many blood cells are produced in the bone marrow; myeloma affects plasma cells, cells that produce immunogobulins (antibodies) that help fight infection and disease.

In multiple myeloma, normal plasma cells transform into malignant myeloma cells and produce large quantities of an abnormal immunoglobulin called monoclonal (M) protein. The malignant cells also 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, also called osteolytic lesions, and other signs of bone loss are common, although they do not occur in all individuals with myeloma.