Multiple myeloma is a cancer that forms in a type of white blood cell called a plasma cell. When signs and symptoms do occur, they can include: Bone pain, especially in your spine or chest Nausea Constipation Loss of appetite Mental fogginess or confusion Fatigue Frequent infections Weight loss Weakness or numbness in your legs Excessive thirst Risk factors Factors that may increase your risk of multiple myeloma include: Increasing age. Your risk of multiple myeloma increases as you age, with most people diagnosed in their mid-60s. Male sex. Men are more likely to develop the disease than are women. Black race. Black people are about twice as likely to develop multiple myeloma as are white people. Family history of multiple myeloma. If a brother, sister or parent has multiple myeloma, you have an increased risk of the disease. Personal history of a monoclonal gammopathy of undetermined significance (MGUS). Every year 1 percent of the people with MGUS in the United States develop multiple myeloma.