The comparison of RA patients with and without CLD showed that RF IgA was associated with ILD (mean ± standard deviation: 206.6 ± 400.5 vs. 95.0 ± 523.1 U/ml, respectively, P = 1.13 × 10− 8), particularly usual interstitial pneumonia (UIP) (263.5 ± 502.0 U/ml, P = 1.00 × 10− 7). Here, CD79A is linked to idiopathic pulmonary fibrosis.