Fibromyalgia--from syndrome to disease. Overview of pathogenetic mechanisms.

According to the classification criteria proposed by the American College of Rheumatology, fibromyalgia is a long-standing multifocal pain condition combined with generalised allodynia/hyperalgesia. It is the generalised allodynia/hyperalgesia that distinguishes fibromyalgia from other conditions with chronic musculoskeletal pain. Central sensitisation of nociceptive neurons in the dorsal horn due to activation of N-methyl-D-aspartic acid receptors and disinhibition of pain due to deficient function of the descending inhibitory system are probable pathogenic factors for allodynia/hyperalgesia. Furthermore, chronic pain is a chronic emotional and physical stressor. Chronic stress and chronic sleep disturbance are not specific for fibromyalgia but could be the causes of symptoms like fatigue, cognitive difficulties and other stress-related symptoms. They may also cause neuroendocrinological and immunological aberrations.