Environmental and occupational exposures in eosinophilic granulomatosis with polyangiitis. A case-control study

Abstract

Background and aims of the study. Eosinophilic granulomatosis with polyangiitis (EGPA, formerly Churg-Strauss Syndrome) is a rare systemic disease, included in the group of antineutrophil cytoplasmic antibodies (ANCA)-associated vasculitis (AAV), characterized by adult-onset asthma, blood and tissue eosinophilia with organ involvement, and small-vessel vasculitis. The disease pathogenesis is poorly understood. Immunogenetic factors may predispose to the disease. However, it has been suspected that the disease may be triggered by exogenous factors including environmental agents, infections, vaccinations, and drugs. Data about the association between individual, environmental and occupational risk factors and the development of EGPA are scarce. In this study we aimed to investigate the role of occupational agents (such as silica, farming, organic solvents and chemical agents) as well as individual agents (such as smoking habits) and their interactions, as potential risk factors for EGPA. Patients and methods. The study has a case-control design. We enrolled 111 patients with EGPA and 333 healthy controls, matched for age, sex and geographical origin. Occupational history was obtained using a structured questionnaire administered by blinded specialists in occupational medicine. The exposures to nonoccupational risk factors potentially predisposing to EGPA were assessed through the interview and through the examination of medical records. All exposures were considered until the time of EGPA diagnosis. Results. EGPA was associated with silica exposure (OR 2.26 [95% CI 1.10-4.62], p=0.026), farming (OR 2.10 [95% CI 1.19-3.73], p=0.011) and with the exposure to organic solvents (OR 2.20 [95% CI 1.14-4.2], p=0.018) at a multivariate analysis. There was a positive relationship between the duration of exposure to silica, chemical agents and the risk of developing EGPA. A multiplicative effect on risk was found for the co-exposure of silica and farming (OR 7.49 [95% CI 2.77-20.25], p<0.0001). The exposure to tobacco smoke appeared protective against EGPA (OR 0.49 [95% CI 0.29-0.70], p<0.0001). Conclusions. This is, to our knowledge, the first study investigating the role of environmental, occupational and individual risk factors in the development of EGPA, through the comparison of a group of EGPA patients with a group of healthy controls, matched for age, gender and geographical origin. Our results demonstrate that occupational factors may significantly contribute to the development of the disease. In particular, we found a significative association between exposure to silica, farming, organic solvents and EGPA. In addition, our findings reveal that tobacco smoking has a protective role against the disease. Further studies are necessary to investigate the biological effects of such risk factors on disease pathogenesis.