Association of rare single-nucleotide variant MUC5B rs35705950 with interstitial lung disease in Japanese rheumatoid arthritis

Objectives RA is sometimes complicated by interstitial lung disease (ILD) with a poor prognosis. A single-nucleotide variant (SNV) in MUC5B was associated with ILD in European RA patients. However, associations of this SNV were not found in Japanese RA patients, because its frequency in Japanese populations is very low. We investigated the associations of candidate SNVs including the MUC5B variant with ILD in Japanese RA.Methods Genotyping of MUC5B rs35705950, MUC2 rs7934606, MAD1L1 rs12699415 and PPFIBP2 rs6578890 in Japanese RA patients was conducted for association analyses.Results MUC5B rs35705950 was associated with usual interstitial pneumonia (UIP) (P = 0.0039, Pc = 0.0156, odds ratio [OR] 10.66, 95% CI 2.05-55.37) or ILD (P = 0.0071, Pc = 0.0284, OR 7.33, 95% CI 1.52-35.44) in Japanese RA under the allele model. MUC2 rs7934606 was associated with UIP (P = 0.0072, Pc = 0.0288, OR 29.55, 95% CI 1.52-574.57) or ILD (P = 0.0037, Pc = 0.0148, OR 22.95, 95% CI 1.27-416.13) in RA. Haplotype analyses suggested the primary association of MUC5B rs35705950 with UIP in Japanese RA. No significant association of MAD1L1 rs12699415 or PPFIBP2 rs6578890 with UIP, nonspecific interstitial pneumonia, or ILD in RA was observed.Conclusion MUC5B rs35705950 is associated with, and might be involved in the pathogenesis of ILD, especially UIP, in Japanese RA.