Myeloma is cancer of the plasma cells. Plasma cells are white blood cells that produce disease- and infection-fighting antibodies in your body. Myeloma cells prevent the normal production of antibodies, leaving your body's immune system weakened and susceptible to infection. The multiplication of myeloma cells also interferes with the normal production and function of red and white blood cells. An abnormally high amount of these dysfunctional antibodies in the bloodstream can cause kidney damage. Additionally, the myeloma cells commonly produce substances that cause bone destruction, leading to bone pain and/or fractures.