A cancer of plasma cells. The plasma cells are a type of white blood cell in the bone marrow. With this condition, a group of plasma cells becomes cancerous and multiplies. The disease can damage the bones, immune system, kidneys and red blood cell count. Symptoms may not be present or may be non-specific, such as loss of appetite, bone pain and fever. Treatments include medication, chemotherapy, corticosteroids, radiation or a stem-cell transplant.