Rheumatoid arthritis (RA) is a systemic autoimmune disorder with a variety of extra-articular manifestations. The lung is a common target and diffuse parenchymal lung disease can appear as any of the patterns found with idiopathic interstitial pneumonia. Controversy exists as to the prognostic significance of these patterns among patients with RA-ILD.
We retrospectively identified 48 patients with a diagnosis of RA-ILD confirmed by surgical lung biopsy. The pathology was reviewed by four expert pulmonary pathologists. We examined survival after stratifying on the presence or absence of fibrotic ILD, and contrasted it with a matched idiopathic pulmonary fibrosis (IPF) population. The Cox proportional hazards model was used to identify independent predictors of survival.
The majority of subjects were male smokers with physiologic restriction. A usual interstitial pneumonia (UIP)-pattern was identified in 31% of subjects. Median survival time for the entire cohort was 1360 days. Subjects with fibrotic ILD had worse survival than subjects with non-fibrotic ILD (log rank p = 0.02). There was no difference in survival between UIP-pattern RA-ILD subjects and IPF controls (log rank p = 0.94). Multivariable analysis revealed that age (hazard ratio [HR] = 1.04, p = 0.01) and fibrosis (HR = 2.1, p = 0.02) were independent predictors of mortality.
Both cellular and fibrosing ILD patterns are common among RA-ILD patients who undergo surgical lung biopsy. These patients have a shortened survival when compared to the general population and all-comers with RA. Age and the presence of a fibrosing interstitial pneumonia predict shortened survival in these patients. Survival in UIP is similar to matched IPF patients.