Caplan's Syndrome Related to Rheumatoid Factors

The rheumatoid pneumoconiosis syndrome was originally described as a characteristic chest radiographic appearance in coal-workers associated with clinical rheumatoid arthritis (Caplan, 1953). This association was later confirmed as real and not fortuitous by Miall, Caplan, Cochrane, Kilpatrick, and Oldham (1953) using an unselected population. The original communication defined the radiographic picture as one showing multiple, welldefined round opacities 0.5 to 5 cm. in diameter distributed throughout the lung field. We will call this the classical appearance. It was noted that cavitation and calcification of the opacities was frequent. There was a tendency for the opacities to appear suddenly before, coincident with, or after the onset of arthritis. Reference was also made to the fact that only a few round opacities may be present, and in many instances the lesions become confluent and may be indistinguishable radiographically from progressive massive fibrosis. It was suggested that more cases would be recognized if it were realized that there is often a mixed radiographic picture of round opacities and opacities indistinguishable from progressive massive fibrosis and tuberculosis. Subsequent observations on more than 550 cases of the syndrome have confirmed in the main the original radiographic description and in particular emphasized the high incidence of cavitation as a characteristic feature. Additional experience among coal-workers has suggested an association of clinical rheumatoid arthritis with discrete nodular opacities 0.3 to 1 cm. in diameter, i.e., somewhat smaller than was originally found, and classifiable under the International Classification of Radiographs of Pneumoconiosis (I.L.O., 1959) as categories 1, 2, or 3 nodular simple pneumoconiosis. Furthermore, even in the absence of clinical arthritis, the sensitized sheep cell agglutination test (S.S.C.A.T.) in these cases, and in others with a mixed nodular and progressive massive fibrosis picture, was found to be positive