Among 126 patients with MPO-ANCA nephritis, 31 (24.6%) had a UIP or probable UIP pattern, 8 (6.3%) had findings indeterminate for a UIP pattern, and 27 (21.4%) had pulmonary infiltrations suggestive of a diagnosis other than UIP (alternative diagnosis). Here, MPO is linked to idiopathic pulmonary fibrosis.