Many factors have been associated with the development of ILD in patients with RA, including older age, male sex, smoking history, seropositivity for rheumatoid factor (RF) or anti-cyclic citrullinated peptide (CCP), elevated erythrocyte sedimentation rate (ESR), moderate or high RA disease activity, and the MUC5B promoter variant [3, 7, 28–33]. The gene discussed is MUC5B; the disease is rheumatoid arthritis.