Unexplained pain and aches have been well known for centuries. In the modern time the concept fibrositis/ fibromyalgia has been applied to the phenomenon of idespread pain without known aetiology. Fibromyalgia (FM) is characterised by widespread, diffuse pain that is moving around. Typical for this condition is also morning stiffness and non restorative sleep, positive tender points (TP) and a number of associated, unspecific symptoms as feeling of swollenness, headache, depression etc.Positive TP are defined anatomic locations that feel painful when being palpated with a pressure of 4 kg/cm2. The TP have been considered as the hallmark of FM and is central in the classification criteria constructed to identify the disease (ACR-90 criteria).FM is not considered as a specific disease entity, but rather a continuum with respect of pain distribution, number of positive TP and number and intensity of associated symptoms. Nevertheless, due to the often overwhelming impact of pain and fatigue in those who fulfil the criteria, it is appropriate to keep FM as a diagnosis.During the last two decades about a dozen epidemiological studies has been performed to describe the prevalence in the general population. The average results lie between three and four percent with a range from 1.2% to 6.6%. The differences is probably mainly due to discrepancies in applied methodology, but one cannot rule out that some populations may have more FM than others. Incidence is not well known, one study performed on women indicates a high incidence.Mortality has until recently not been studied. There are now some few studies with somewhat scattered results. However, the major finding is higher mortality among individuals with FM, especially due to cancer.Whether this is a function of lifestyle or the presence of pain remains to be clarified. The main risk factor is the female gender; only about 10-30% of the FM population are men. Studies have shown that depression, longstanding localised pain especially in the back and the presence of a relatively large number of associated symptoms also are risk factors. FM develops in the majority of cases over many years. This knowledge may contribute to prevent FM before it actually manifests as such. FM has a large co-morbidity, especially with inflammatory rheumatological diseases. It is important to be aware of this to avoid overtreatment in patients with longstanding inflammatory diseases that have developed FM in addition. On the other hand it is also important to know that patients with FM also may get inflammatory diseases. It is an especially big overlap between FM and Sj?gren’s syndrome. FM is a frequent condition that has a big impact on working ability. In Norway about five present of all who are receiving disability pension do have the diagnosis of FM. In spite of that approximately 50% of females’ application for disability pension are refused, FM is the most common diagnosis among those who are receiving pension. The development of the criteria has opened for international research on a considerable scale. This has lead to better understanding of the aetiopathogenesis and promising treatment possibilities in the future.
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