Plasma cells are one form of the white blood cells that the body manufactures to fight infection.
Although multiple myeloma weakens the bones, it is not the same as bone cancer. The horde of excess plasma cells also tends to discourage production of other white blood cells, leaving the body vulnerable to infections. And the disease may also damage the kidneys, eventually leading to kidney failure. Causes There is no known cause. However, we do know that the disease usually strikes after age 40, and that certain factors increase your odds of developing it.