In your bone marrow, specifically in the lymphoid tissue, live a variety of lymphoid cells. Their main role is to secrete immunoglobulins (antibodies) to fight infection and other pathogenic conditions. This work must be done constantly to keep you body healthy. Multiple myeloma occurs when, due to certain factors, plasma cells multiply excessively in several regions of the bone marrow. Instead of producing normal antibodies (immunoglobulin) to protect your organism, myeloma cells produce an abnormal immunoglobulin called monoclonal protein (or M protein).
In addition, this disorder can result in formation of cells called osteoclasts. Osteoclasts are cells responsible for bone resorption. They act by lowering the pH in contact with the bone matrix and secreting proteolytic enzymes, leading to a deterioration in the bone structure and increased risk of fractures and pain.