In order to evaluate the association between the 6MWT, serum levels of Krebs von den Lungen-6 (KL-6), and spirometry parameters, including lung volumes and DLCO, with HRCT findings suggestive of ILD in RA, we conducted a cross-sectional observational study at a tertiary rheumatology center in Brazil. This evidence concerns the gene MUC1 and rheumatoid arthritis.