Some patients with autoimmune characteristics and idiopathic interstitial pneumonia (IIP), particularly usual interstitial pneumonia (UIP), do not fit neatly into the category of connective tissue disease associated interstitial lung disease (CTD-ILD), idiopathic pulmonary fibrosis (IPF) or recently proposed yet to be validated criteria for interstitial pneumonia with autoimmune features (IPAF). Outcomes of these patients are unknown.
Retrospective single center study; ANOVA analyses compared differences in mean change in forced vital capacity (FVC) and diffusion capacity (DLCO) over 1-year among 124 well defined patients (20 AI-ILD [positive autoantibodies with or without symptoms of CTD], 15 IPAF, 36 CTD-ILD, 53 “Lone-IPF” [patients with IPF without any autoantibodies])
75% of patients with AI-ILD, 33% IPAF, and 33% CTD-ILD had UIP. Initial FVC and DLCO were similarly moderately reduced across groups. Mean change in FVC: -60 mL IPAF, -110 mL AI-ILD, -10 mL CTD-ILD, -90 mL Lone-IPF (p=0.52); Mean change in DLCO (mL/mmHg/min): 2.39 IPAF, -1.15 AI-ILD, -0.27 CTD-ILD, -1.05 Lone-IPF (p < 0.001) over 12 months. By pattern of disease mean change in FVC: -140 mL UIP, 10 mL NSIP, 12 mL unclassifiable/other (p=0.001).
No clinically significant differences in pulmonary function to distinguish between patients with AI-ILD, IPAF, CTD-ILD and Lone-IPF were observed after 1 year. Longer periods of follow up are needed to understand the outcomes of these patients. It is not yet clear whether AI-ILD is a distinct phenotype or a variant of the newly proposed entity IPAF.