Multiple myeloma is cancer in plasma cells, which are a type of white blood cell. The cancer cells crowd out normal cells in the bone marrow, causing problems like anemia and bleeding. The cancer cells can also weaken bone and form tumors in the bone or other areas.

Healthy plasma cells make antibodies that help fight infection. But myeloma plasma cells make abnormal antibodies. This can make it hard for your body to fight infection and can cause problems with the kidneys.

Symptoms include feeling very tired and weak, bruising or bleeding easily, bone damage and pain, kidney problems, and getting fevers and infections more often.

Multiple myeloma that isn't causing symptoms may not need treatment right away. Treatments include radiation therapy, surgery, and medicines, such as targeted therapy, chemotherapy, and immunotherapy. Stem cell transplants may also be used.