In the genetic association analysis, the SNPs rs35705950 (MUC5B) and rs111521887 (TOLLIP) were significantly associated with RA with PF, compared with population controls [for rs35705950: OR 4.4 (95% CI 1.9, 11.0), adjusted P-value = 0.00069, q-value = 0.009; for rs111521887: OR 2.4 (95% CI 1.2, 4.5), adjusted P-value = 0.0083, q-value = 0.054; Table 2a]. Here, MUC5B is linked to rheumatoid arthritis.