Conceptual evolution of fibromyalgia Until recently, the lack of a unifying etiology (the study of the causes and origins of the condition), and the lack of an accepted terminology, has hindered the understanding and recognition of fibromyalgia. Over the years, fibromyalgia has undergone a "conceptual evolution" (21). Early fibromyalgia studies Descriptions of fibromyalgia can be found dating back to the early 1800’s. In 1904, pathologist Ralph Stockman first reported evidence of inflammatory changes in the fibrous, intra-muscular septa (a thin membrane that divides two soft masses of tissue) on biopsies from patients (3). Also in 1904, Sir William Gowers introduced the term "Fibrositis" to describe the inflammation of fibrous tissue in his description of low back pain. However, subsequent studies of muscle biopsies have failed to reproduce Stockman’s findings of inflammation, and the term "fibrositis" is therefore considered a misnomer. In subsequent years, the terms fibrositis, fibromyositis, psychogenic, psychosomatic, or muscular rheumatism have all been used as descriptors for this syndrome. Yet the term fibrositis has been most resilient and "eventually became synonymous with idiopathic local or diffuse musculoskeletal pain of any type" (6). Moder classification of fibromyalgia In the 1970’s, the researcher Hench first introduced the term "fibromyalgia". He noted that "muscle as well as ligamentous and tendonous connective tissues are usually subjectively involved." Subsequently, in the 1980’s, another researcher, Yunus, furthered clarification of fibromyalgia by proposing the need for a unified classification system as well as the first diagnostic criteria (8). Finally, in 1990, the American College of Rheumatology established firm criteria for the classification and diagnosis of fibromyalgia (9).