Lindberg H, Colliander C, Nise L, et al. - In this study the possible relationship between animal exposure and risk for granulomatosis with polyangiitis (GPA) was explored. Between January 1, 2011, and December 31, 2018, researchers included patients with GPA at the Department of Rheumatology, Uppsala University Hospital. As controls, researchers enrolled 128 patients with rheumatoid arthritis and 248 population controls collected from the Epidemiological Investigation of Rheumatoid Arthritis study, matched for age, gender, and geographical area of residence. A significant correlation was found between exposure to specific animals, namely horses, and the development of GPA. The outcomes also support previous studies demonstrating a relationship between farming and GPA, underscoring the possibility of exogenous factors as initiators in the development of GPA.