MUC1 and interstitial lung disease: AD + group was older than AD– (65.8 ± 11.6 vs. 58.8 ± 14.6 years old, p < 0.001), had a lower proportion of females (69.6 vs. 78.3%, p = 0.029), longer RA duration (11.5 ± 15.2 vs. 7.3 ± 12.0 years, p = 0.003), lower body mass index (BMI) (20.9 ± 4.2 vs. 22. ± 3.9, p = 0.002), higher incidence of ILD (44.4 vs. 12.4%, p < 0.001), higher serum level KL-6 (485 ± 373 vs. 387 ± 442 U/ml, p < 0.001), and lower eGFR (84.2 ± 28.3 vs. 90.4 ± 28.9 ml/min/1.73m2, p = 0.014).