MPO and idiopathic pulmonary fibrosis: Moreover, although most reports mentioned that UIP pattern was the main pattern on high-resolution computed tomography (HRCT), an overlapping or indeterminate pattern (i.e., unclassifiable pattern other than UIP, non-specific interstitial pneumonia, and organizing pneumonia) may present to some extent in the MPO-ANCA-positive population with ILD because pathologically, MPO-ANCA-positive patients with ILD showed more prominent inflammatory cell infiltration and cellular bronchiolitis [2, 6].