Is fibromyalgia a distinct clinical entity? Historical and epidemiologicalevidence

Most medical specialities have defined medically unexplained syndromes such as fibromyalgia, to categorize patients with prominent but unexplained sym ptoms. Other such syndromes include irritable bowel syndrome, chronic fatig ue syndrome and atypical chest pain. In this chapter we present evidence to suggest that fibromyalgia is not a unique clinical entity, but shares much with these other syndromes. We use historical, clinical and epidemiologica l evidence to illustrate this idea. The historical data emphasize the essen tially arbitrary way in which fibromyalgia developed. The clinical evidence shows the considerable overlap between patients with fibromyalgia and thos e with other unexplained syndromes. From an epidemiological perspective we emphasize the strong associations between symptoms such as myalgia and fati gue. We conclude by suggesting that fibromyalgia is one of many medically u nexplained syndromes which have more similarities than differences between them.