MPO and interstitial lung disease: The major causes of death in patients with MPO-ANCA-positive ILD were acute exacerbation (AE) of ILD (10–25.5%), chronic progressive fibrosing ILD (PF-ILD) (7.8–19%), infectious disease (19.2–20%), and diffuse alveolar hemorrhage (DAH) (4.3–30%) [10,11,31].