Chronic Fatigue Syndrome (CFS), also known as myalgic encephalomyelitis (ME) or systemic exertion intolerance disease (SEID), is a disorder characterized by extreme tiredness. Symptoms of CFS include profound or extreme fatigue, extreme exhaustion lasting more than 24 hours after physical or mental exercise, sleep abnormalities, including unrefreshing sleep, and unexplained joint or muscle pain. There is no known genetic cause for CFS; however, researchers areactively studyingthis avenue as there may be someevidence for a heritable predisposition. Possible genetic conditions that share similar symptoms with CFS are Fanconi Anemia and Hereditary Hemochromatosis.