Given a reference text about multiple myeloma, tell me the risk factors and the cause of the disease.

Multiple myeloma (MM), also known as plasma cell myeloma and simply myeloma, is a cancer of plasma cells, a type of white blood cell that normally produces antibodies.[6] Often, no symptoms are noticed initially.[10] As it progresses, bone pain, anemia, kidney dysfunction, and infections may occur.[10] Complications may include amyloidosis.[3]

The cause of multiple myeloma is unknown.[4] Risk factors include obesity, radiation exposure, family history, and certain chemicals.[5][11][12] There is an increased risk of multiple myeloma in certain occupations.[13] This is due to the occupational exposure to aromatic hydrocarbon solvents having a role in causation of multiple myeloma.[14] Multiple myeloma may develop from monoclonal gammopathy of undetermined significance that progresses to smoldering myeloma.[15] The abnormal plasma cells produce abnormal antibodies, which can cause kidney problems and overly thick blood.[10] The plasma cells can also form a mass in the bone marrow or soft tissue.[10] When one tumor is present, it is called a plasmacytoma; more than one is called multiple myeloma.[10] 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.[6] Another common finding is high blood calcium levels.[6]

Although the cause of multiple myeloma is not known, risk factors for developing the disease are obesity, radiation exposure, family history, and exposure to certain chemicals.