Epidemiology of scleroderma.
The rarity of scleroderma makes it a difficult disorder to study epidemiologically. Recent studies have highlighted some of the environmental exposures associated with the disease. Among occupational exposures silica remains the most important, whereas appetite suppressants might be an important drug cause. The disease also appears to cluster in space, with one report suggesting that proximity to airports might be important. There has been considerable recent attention given to a scleroderma-like syndrome developing after ingestion of L-tryptophan; the link seems definite and the latter's subsequent withdrawal indicates that this might become of historic interest only. The relevance for "sporadic" scleroderma is unclear. Interest has also focused on survival and its predictors. It is clear that scleroderma is associated with a substantially reduced survival and that the extent of skin involvement and the development of internal organ involvement, particularly renal and pulmonary, are the worst prognostic features.