Background Patients with interstitial lung disease (ILD) who show features related to autoimmunity without meeting criteria for a defined connective tissue disease are categorized as interstitial pneumonia with autoimmune features (IPAF). The present study compared clinical characteristics and clinical outcomes of patients with IPAF to patients with connective tissue disease related-interstitial lung disease (CTD-ILD) and patients with idiopathic pulmonary fibrosis (IPF). Methods ILD patients who were consecutively enrolled in a single institution ILD cohort between 2008 and 2015 were evaluated for the study. Clinical data had been prospectively collected, while radiologic imaging and pathologic findings were re-reviewed for the present study. Results Out of 305 patients with ILD, 54 (17.7%) patients met the classification of IPAF, 175 (57.4%) patients had IPF, and 76 (24.9%) patients were diagnosed with CTD-ILD. Compared to IPF, incidences of acute exacerbations in 1,3 and 5 years were significantly less in the IPAF group ( p = 0.022, p = 0.026 and p = 0.007, respectively). From multivariate analysis for mortality, age ( p = 0.034, HR 1.022, 95% CI: 1.002–1.044), FVC ( p < 0.001, HR 0.970, 95% CI: 0.955–0.984), ILD exacerbation ( p = 0.001, HR 2.074, 95% CI: 1.366–3.148), and ILD type ( p = 0.047, HR 0.436, 95% CI: 0.192–0.984 (IPAF vs IPF), respectively) showed significant association. Conclusions Compared to the other ILD groups, IPAF showed distinct clinical characteristics. The IPAF group showed better survival and less episodes of exacerbation when compared to the IPF group.

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