Fibromyalgia is a term referring to pain in the fibrous tissues of the body, such as muscles, tendons, and ligaments.
Fibromyalgia syndrome (FMS) is a form of fibromyalgia where pain and stiffness occurs in muscles, tendons, and ligaments throughout the body, accompanied by other generalized symptoms such as fatigue, sleep disruption or unrefreshing sleep, mood disorder, and cognitive difficulties such as poor memory or mental "fogginess." The cause is not known. It is most common in middle-aged women, but can affect people of all ages and both sexes.
Depression, anxiety, and sleep disturbances have all been linked to fibromyalgia.