Scleroderma in South Australia: epidemiological observations of possible pathogenic significance

Background: Scleroderma is an autoimmune disorder of unknown cause. Previou s epidemiological studies have suggested some regional clustering and assoc iations with occupations involving exposure to silica dusts and hydrocarbon s. Aims: To determine: (i) prevalence and incidence of scleroderma in South Au stralia (SA), a state with a stable population living in well-defined urban , rural and industrial regions, (ii) hospital separation rates, (iii) cumul ative survival rates, (iv) gender and disease subclassification, (v) geogra phical residency and occupations, (vi) familial associations and (vii) age at onset versus age-specific incidence rate. Methods: Creation of the South Australian Scleroderma Register (SASR) to id entify demographics and clinical and serological features of all scleroderm a patients resident in SA. Results: Scleroderma occurs in South Australia with a point prevalence of 2 3 per 10(5) and an incidence of approximately 1/15th of this. However, this prevalence is high compared with other regional world studies. Scleroderma is predominantly a female disease, with most patients having the limited f orm of scleroderma characterized by the presence of the anticentromere anti body and a mean survival of 27.6 years. In contrast, diffuse scleroderma is a less benign disease occurring at an early age of onset and has a mean su rvival of 9.6 years. Scleroderma occurs throughout SA without regional loca lization. Weak associations are seen in males, but not females, with occupa tions involving possible environmental exposure to silica or hydrocarbons. Scleroderma rarely occurs in families. Conclusion: No strong genetic or environmental influences were found to acc ount for the relatively common occurrence of scleroderma in SA. The age at onset versus age-specific incidence curve suggests that scleroderma can be considered as a stochastic illness involving a number of random events occu rring in a predisposed population. These random events may involve mutation s of pivotal somatic genes.