Occupational exposures and smoking in eosinophilic granulomatosis with Polyangiitis (Churg-strauss syndrome).

OBJECTIVE Eosinophilic granulomatosis with polyangiitis (EGPA, formerly Churg-Strauss syndrome) is a rare anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis. Environmental agents and occupational exposures may confer susceptibility to EGPA, but data are scarce. We investigated the association between occupational exposures (e.g., silica, farming, asbestos, organic solvents) and other environmental agents (e.g., smoking) and the risk of EGPA. METHODS One-hundred and eleven newly diagnosed EGPA patients and 333 controls matched for age, sex and geographic area of origin were recruited at a national referral centre for EGPA. Exposures were assessed using a dedicated questionnaire administered by a blinded specialist in occupational medicine. RESULTS Exposures to silica [OR 2.79 (95% CI 1.55-5.01), p=0.001], organic solvents [OR 3.19 (95% CI 1.91-5.34), p<0.001], and farming [OR 2.71 (95% CI 1.71-4.29), p<0.001] were associated with an increased risk of EGPA. Co-exposure to silica and farming yielded an OR of 9.12 (95% CI 3.06-27.19) (p<0.001), suggesting a multiplicative effect between these two exposures. Smoking (current and former smokers combined) was significantly less frequent among cases than among controls [OR 0.49 (95% CI 0.29-0.70), p<0.001)]. The pack-year index was also lower among cases [OR 0.96 (95% CI 0.94-0.98), p<0.001]. The associations with silica and farming were primarily aligned with ANCA-positive EGPA, those with smoking and solvents with ANCA-negative EGPA. CONCLUSION The environment influences the susceptibility to EGPA: exposures to organic solvents, silica, and farming are associated with an increased risk of the disease, while smoking with a lower risk. These exposures seem to have distinct effects on EGPA subsets.