Abstract Background and Aims Exposure to silica is associated with an increased risk of autoimmune diseases, including ANCA-associated vasculitis (AAV) [1–3]. It remains unclear whether silica exposure modifies clinical presentation of AAV, and it is not known whether it affects prognosis. The aim of this work is to address these questions. Method This is a retrospective, monocentric observational study comparing clinical and prognostic features between two groups of patients with ANCA-positive AAV: cases with a well-documented history of occupational exposure to silica (confirmed by industrial hygienists) and controls with no exposure. Each case was matched to 2 controls based on time of diagnosis (± 1 year relative to the case). Clinical features were compared across the two groups using Student's t test or chi-squared test, as appropriate. Clinical outcomes were compared across groups with the log-rank test and Cox proportional hazards regression. Results We identified 25 patients with AAV and a clear-cut history of occupational exposure to silica and 50 controls with no exposure, diagnosed between 2000 and 2023. Compared to controls, patients exposed to silica were more frequently males and smokers (Table). Average age at presentation was 66 ± 14 years and most patients had microscopic polyangiitis and MPO-ANCAs, with no significant differences according to silica exposure (Table). Patterns of organ involvement were also comparable across the two groups (Table). Renal vasculitis was present in almost all patients, probably reflecting a referral bias. Severity of renal impairment at diagnosis (Table) and evolution to end stage renal disease (Figure) were similar between exposed and unexposed individuals. There was a trend for lower survival in patients with exposure to silica (median survival from AAV diagnosis: 172 months in cases and 111 months in controls, log-rank test p = 0.065, Figure). In multivariate Cox regression, the risk of death was independently associated with age at diagnosis (HR 1.09 per year, 95% CI 1.04-1.14, p < 0.001) and not with silica exposure (HR 0.96, 95% CI 0.39-2.41, p = 0.936) or smoking history (HR 2.06, 95% CI 0.80-5.33, p = 0.135). Conclusion Patients with AAV and exposure to silica were more frequently males and smokers, likely reflecting socio-economic factors. We did not identify otherwise distinct clinical features in exposed patients, similarly to other Authors such as Hogan et al [2]. Exposure to silica did not seem to significantly affect renal prognosis or survival either, despite a trend in univariate analysis for higher mortality in individuals with silica exposure. The limited sample size and lack of quantification of silica exposure must be acknowledged and may have reduced statistical power.
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Jun 1, 2024
Rene Leblanc 
Open Access