Is fibromyalgia a distinct clinical entity? Pain mechanisms in fibromyalgia syndrome. A myologistʹs view

The cause of muscle pain and allodynia may not be the same in all persons fulfilling the American College of Rheumatology (ACR) criteria for fibromyalgia syndrome. In the majority of patients the generalized pain is preceded by localized or regional pain, usually in the musculoskeletal system. In many patients with fibromyalgia there are findings compatible with tissue injury pain with pain mechanisms involving both the primary afferent neuron and the nociceptive system in the central nervous system. Evidence for these mechanisms is described.