Multiple myeloma is a blood cancer of the plasma cells and develops in the bone marrow, the soft spongy tissue found in the center of the bones. In addition to plasma cells, bone marrow also contains other blood cells, such as red cells, white cells, and platelets.
Plasma cells in a healthy individual create antibodies that help the body fight off infections and other diseases. In a person with multiple myeloma, the cancerous plasma cells make an abnormal antibody, called a monoclonal protein, or M protein, which can also be called an M-spike, monoclonal immunoglobulin, or paraprotein. The M protein builds up and pushes out the red cells, white cells, and platelets in the bone marrow.
Because there is less room for normal blood cells in the bone marrow, bone damage may occur causing bone pain, osteolytic lesions, which are weak spots on the bones, fractures, or increased levels of calcium in the blood, called hypercalcemia. Decreased blood cell numbers can also cause anemia, excessive bleeding, and a decreased ability to fight off germs or infections. The M protein buildup has the ability to cause kidney damage or damage to other organs if it accumulates too much in the blood or urine.
Continued research is being done to understand exactly how multiple myeloma forms, but the exact reasoning has not yet been determined. While some mutations have been identified as genetic risk factors, multiple myeloma is not considered a hereditary disease and genetic mutations can vary from person to person.
Multiple myeloma is categorized into three stages, stage I, stage II, or stage III. Stage I is typically less aggressive, while stage III is the most aggressive. Classifying multiple myeloma by stage can lead to a better understanding of the best course of treatment or risk associated with the disease.