In addition to its role as an autoantigen in WG, PR3 is known to have a diverse range of activities in the regulation of inflammation, including degradation of extracellular matrix proteins [23], potentiation of platelet activation [25] and processing proinflammatory cytokines and receptors to mature forms (TNF-α, IL-1β, TGF-β, IL-18 [26–28]). Here, PRTN3 is linked to granulomatosis with polyangiitis.