Clinical Characteristics and Natural History of Autoimmune Forms of Interstitial Lung Disease: A Single-Center Experience

Objective To describe the phenotypic characteristics and natural history of patients with autoimmune forms of interstitial lung disease (ILD). Methods Retrospective, descriptive, single-center study of patients with autoimmune forms of ILD evaluated between February 2008 and August 2014. All data were extracted from the electronic medical record. Longitudinal changes in forced vital capacity (FVC%) and diffusion capacity for carbon monoxide (DLco%) in percent predicted were analyzed and time-to-event analyses for death were performed using Cox regression. Results Of the entire cohort (n = 243), systemic sclerosis (SSc)-associated ILD (n = 88, 36%), interstitial pneumonia with autoimmune features (IPAF, n = 56, 23%), rheumatoid arthritis (RA)-associated ILD (n = 42, 17%), and idiopathic inflammatory myopathy (IIM)-associated ILD (n = 26, 11%) were the most common phenotypes. The SSc-ILD, IIM-ILD, and IPAF groups had similar features: average age in the mid-50s, strongly female predominant and more likely to have nonspecific interstitial pneumonia (NSIP). In contrast, RA-ILD patients were older, gender balanced, more likely to be past smokers and were UIP predominant. Adjusted longitudinal lung function was stable during a median follow-up period of nearly 4 years and the independent predictors for death were older age (p = 0.003), male sex (p = 0.019), and lower FVC (p = < 0.001). Conclusions The predominant phenotypes of autoimmune ILD were SSc-ILD, IPAF, RA-ILD, and IIM-ILD. In contrast to the other subsets, those with RA-ILD may be older, gender balanced, with more smoking history, and higher proportion of UIP. Longitudinal lung function was stable among the groups and younger age, female gender, and better lung function were associated with improved survival.