“…It is the experience of most rheumatologists that at the outset there may be several features characteristic of more than one rheumatic disease, or sometimes during the course of the disease, there may be a progression of one rheumatic disease syndrome into another. Such 'overlap' syndromes have been described for scleroderma and dermatomyositis (Tuffanelli and Winkelmann et al, 1961;Clark et al, 1971), rheumatoid arthritis and scleroderma (Tuffanelli and Winkelmann et al, 1961;Poirer and Rankin, 1972), SLE and polymyositis (Keil, 1940;Estes and Christian, 1971;Dubois, 1973), rheumatoid arthritis and SLE (Haserick, 1955;Sigler et al, 1958;Toone et al, 1960;Dubois 1962;Dubois, 1974), and scleroderma and SLE (Muehrcke et al, 1957;Tuffanelli and Winkelmann, 1961;Rowell, 1962;D'Angelo et al, 1969;Dubois, et al, 1971;Poirer and Rankin, 1972;Dubois, 1974). Whether such associations represent the co-existence of separate diseases, distinct clinical entities, or the more widespread expression of a single rheumatic disease syndrome, has been a source of some controversy.…”