MPO and idiopathic pulmonary fibrosis: Up to 26% of anti-MPA-positive patients develop MPA with anti-MPO antibodies.[9–12] Significantly few studies have reported the development of granulomatosis with polyangiitis in antiproteinase antibodies positive IPF patients.[14] The most frequently reported clinical manifestations of MPA in the IPF population are rapidly progressive glomerulonephritis, mononeuritis multiplex, diffuse alveolar hemorrhage, and gastrointestinal involvement.[9,12,15]