There are estimates that as high as 4 percent of the adult population in the United States suffers from this little-understood condition and that the vast majority are female--which is the case with most autoimmune diseases like lupus or multiple sclerosis. Fibromyalgia can be extremely debilitating and until recently was dismissed as a phantom disorder, or part of the patient's imagination. The degree of pain and disability from fibromyalgia can range from mild to severe.