Myeloma begins when a plasma cell becomes abnormal. The abnormal cell divides to make copies of itself. These abnormal plasma cells are called myeloma cells. In time, myeloma cells collect in the bone marrow. They may damage the solid part of the bone. When myeloma cells collect in several of your bones, the disease is called "multiple myeloma." This disease may also harm other tissues and organs, such as the kidneys.Myeloma cells make antibodies called M proteins and other proteins. These proteins can collect in the blood, urine, and organs.