Illustration of multiple myeloma cells (translucent with purple nuclei), red blood cells (red discs) and healthy white blood cells (pink nuclei) in the bloodstream. Multiple myeloma is a type of cancer that occurs when a type of white blood cell called a plasma cell becomes abnormal and cancerous. The cancerous plasma cell divides and multiplies creating large amounts of abnormal antibodies. These abnormal antibodies can affect multiple parts of the body, causing pain and weakening of the bones amongst other symptoms. Multiple myeloma is typically incurable but can be treated with immunotherapy, chemotherapy and radiotherapy.