Multiple myeloma (MM), also known as plasma cell myeloma and simple myeloma, is a cancer of plasma cells, a type of white blood cell that normally produces antibodies.Often, no symptoms are noticed initially. As it progresses, bone pain, bleeding, frequent infections, and anemia may occur. Complications may include amyloidosis. The cause of multiple myeloma is unknown.Risk factors include obesity, radiation exposure, family history, and certain chemicals. Multiple myeloma may develop from monoclonal gammopathy of undetermined significance that progresses to smoldering myeloma. The abnormal plasma cells produce abnormal antibodies, which can cause kidney problems and overly thick blood. The plasma cells can also form a mass in the bone marrow or soft tissue. When one tumor is present, it is called a plasmacytoma; more than one is called multiple myeloma. Multiple myeloma is diagnosed based on blood or urine tests finding abnormal antibodies, bone marrow biopsy finding cancerous plasma cells, and medical imaging finding bone lesions. Another common finding is high blood calcium levels.