Symptoms. Multiple myeloma tends to be asymptomatic in its early stages. Symptoms that do occur, particularly in later stages of the disease, include bone pain, frequent infections, fatigue, mental fogginess or confusion and numbness or weakness in the legs. Gastrointestinal issues are also symptomatic of multiple myeloma such as nausea, constipation, loss of appetite and weight loss. Afflicted individuals have a higher risk of broken bones and frequently deal with fatigue.