PR3 antibodies directed against c-ANCA are present in a number of conditions, including granulomatosis with polyangiitis (Wegener’s),13 microscopic polyangiitis, pauci-immune crescentic glomerulonephritis, Churg–Strauss syndrome, cystic fibrosis, inflammatory bowel disease, primary sclerosing cholangitis, and rheumatoid arthritis. Here, PRTN3 is linked to eosinophilic granulomatosis with polyangiitis.