Histopathologic pattern and clinical features of rheumatoid arthritis-associated interstitial lung disease

Study objectives: To investigate the histopathologic pattern and clinical features of patients with rheumatoid arthritis (RA)-associated interstitial lung disease (ILD) according to the American Thoracic Society (ATS)/European Respiratory Society consensus classification of idiopathic interstitial pneumonia. Design: Retrospective review. Setting: Two thousand-bed, university-affiliated, tertiary referral center. Patients: Eighteen patients with RA who underwent surgical lung biopsy (SLBx) for suspected ILD. Method: SLBx specimens were reviewed and reclassified by three lung pathologists according to the ATS/European Respiratory Society classification. Clinical features and follow-up courses for the usual interstitial pneumonia (UIP) pattern and the nonspecific interstitial pneumonia (NSIP) pattern were compared. Results: The histopathologic patterns were diverse: 10 patients with the UIP pattern, 6 patients with the NSIP pattern, and 2 patients with inflammatory airway disease with the organizing pneumonia pattern. RA preceded ILD in the majority of patients (n = 12). In three patients, ILD preceded RA; in three patients, both conditions were diagnosed simultaneously. The majority (n = 13) of patients had a restrictive defect with or without low diffusion capacity of the lung for carbon monoxide (DLCo) on pulmonary function testing; 2 patients had only low DLCO. The UIP and NSIP groups were significantly different in their male/female ratios (8/2 vs 0/6, respectively; p = 0.007) and smoking history (current/former or nonsmokers, 8/2 vs 0/6; p = 0.007). Many of the patients with the UIP pattern had typical high-resolution CT features of UIP. Five patients with the UIP pattern died, whereas no deaths occurred among patients with the NSIP pattern during median follow-up durations of 4.2 years and 3.7 years, respectively. Conclusions: The histopathologic type of RA-ILD was diverse; in our study population, the UIP pattern seemed to be more prevalent than the NSIP pattern.