Multiple myeloma (plasma cell neoplasm) is a rare type of cancer that results in the uncontrolled production of one type of white blood cell (plasma cell) in the bone marrow. The cancer cells can crowd out normal blood cells, causing a reduction in red blood cells (anemia).

The overproduction of plasma cells causes an increase in antibodies. The plasma cells also may cause the bone to break down. The plasma cells can collect in the bone to make small tumors called plasmacytomas.

The most common symptoms of multiple myeloma include night sweats, weight loss, weakness, fatigue, bone pain, pneumonia, numbness, paralysis, or kidney failure. If the bones of the spine are involved, they may collapse, causing spinal cord compression.

The exact cause of multiple myeloma is not known. It is slightly more common in men than in women and is usually diagnosed between the ages of 40 and 70. The disease is very rare before the age of 40.

Multiple myeloma is usually treated with chemotherapy to reduce the numbers of abnormal plasma cells, antibiotics to help fight infection, and pain medication. Radiation therapy may be used to treat bone masses.