Fibromyalgia is a clinical syndrome characterized by the presence of chronic widespread pain accompanied by tenderness and fatigue. Central sensitization is considered to be a major pathogenetic feature of fibromyalgia. While the etiology of fibromyalgia is incompletely understood, it is generally considered to result from the interaction between an appropriate genetic background and the exposure of a susceptible individual to various inciting "triggers". These have included among others physical trauma, infection, stress etc.