MPO and interstitial lung disease: Previous meta-analyses have reported the clinical implications of ILD in patients with AAV: (i) ILD occurs in approximately 23% of patients with GPA and up to 45% of those with MPA; (ii) ANCA positivity might be associated with the concurrent occurrence of ILD in patients with AAV: in particular, MPO-ANCA might be detected in 46-71% of patients with AAV and ILD; (iii) the UIP pattern is predominantly found in patients with AAV ranging from 43% to 83%; and (iv) ILD is likely associated with a relatively high mortality rate in patients with AAV, in particular, those with the UIP pattern [8, 9].