MUC1 and interstitial lung disease: Rheumatoid arthritis-associated ILD illustrates the stakes: affected patients face a threefold increase in mortality compared with those who have RA without lung disease, and many develop progressive pulmonary fibrosis characterized by declining lung function and worsening symptoms (8, 9). A recent prospective study found that more than one-third of RA-ILD patients met criteria for progressive pulmonary fibrosis over three years, with baseline biomarkers like KL-6 and hSP-D helping to identify those at highest risk (10).