Fibromyalgia (Myofascial Pain Syndrome) By Deepan S Dalal, MD, MPH, Brown University Reviewed / Revised Mar 2022 | Modified Sep 2022 View Patient Education Etiology Symptoms and Signs Diagnosis Prognosis Treatment Key Points Fibromyalgia is a common, incompletely understood nonarticular, noninflammatory disorder characterized by generalized aching (sometimes severe); widespread tenderness of muscles, areas around tendon insertions, and adjacent soft tissues; muscle stiffness; fatigue; mental cloudiness; poor sleep; and a variety of other somatic symptoms.