What Is Multiple Myeloma?

Multiple myeloma is a kind of cancer that begins in plasma cells, a type of white blood cell. Plasma cells produce antibodies (immune system proteins) that assist the body in ridding itself of harmful substances. Each plasma cell responds to one specific substance by producing one kind of antibody. The body has many types of plasma cells and can respond to many types of substances.

Multiple myeloma causes the body to overproduce plasma cells, both abnormal and alike. Abnormal plasma cells are called myeloma cells. When plasma cells grow out of control, myeloma cells build up in the bone marrow, in the outer layer of the bone or in organs, causing a variety of problems, including:

  • Tumors that can destroy normal bone tissue, causing bone pain and sometimes fractures.
  • Large amounts of calcium can enter the bloodstream, causing confusion, pain and kidney failure.
  • Cancerous plasma cells can crowd the bone marrow, preventing healthy cells from working normally, specifically:
    • Prohibiting the white blood cells from fighting infection.
    • Inhibiting the production of platelets, which are needed for clotting blood.
    • Overproducing antibodies, which can travel through the blood and damage organs, such as the kidneys.

Multiple myeloma tends to spread through the blood in the form of monoclonal protein. It is found most commonly in the bone marrow and bones, but it can affect the kidneys and immune system. Occasionally, a collection of plasma cells (myeloma cells) may collect in an organ/soft tissue. This is called a plasmacytoma. Some of the most common skeletal areas that may be affected by myeloma cells include the spine, ribs, skull, pelvis and femur.

In rare cases when multiple myeloma spreads outside of the bones, it may go to the soft tissues of the body. Even when myeloma stays in the bone marrow, myeloma cells make an abnormal protein that travels throughout the body and can damage other organs, such as the kidneys.