MUC5B and rheumatoid arthritis: Clinically significant interstitial lung disease (ILD) occurs in roughly 10% of patients with rheumatoid arthritis (RA).1,2 There are limited data on the pathogenesis of RA-ILD; risk factors include smoking, rheumatoid factor or anti-cyclic citrullinated peptide autoantibodies, and genetic variants including MUC5B, HLA-B54, HLA-B40, and HLA-DQ1B*060.