Multiple myeloma is a disorder in which plasma cells are produced in an uncontrolled and invasive (malignant) fashion. Plasma cells develop from lymphocytes, a type of white blood cell. They are found primarily in the bone marrow and lymph nodes.

Plasma cells are responsible for helping the body fight infection. They produce antibodies that circulate in the blood and recognize markers, called antigens, on the cells of invading organisms like bacteria. These antibodies defend the body against foreign organisms.

Multiple myeloma occurs when the plasma cells in the bone marrow begin reproducing uncontrollably. While normal bone marrow contains less than 5% plasma cells, bone marrow in a patient with multiple myeloma contains over 10% plasma cells.

Multiple myeloma tends to be a disease of the elderly. The average patient is 68 years old when diagnosed. During the last 10 years, doctors have seen an increase in cases of multiple myeloma...