This study evaluates the usefulness of serum KL-6, SP-D and TGF-β1 levels in assessing lung impairment and predicting interstitial lung disease (ILD) short-term progression in patients with interstitial pneumonia with autoimmune features (IPAF). A total of 24 patients with IPAF, 21 with connective tissue disease-associated ILD (CTD-ILD) and 23 with CTD without ILD were followed for 1 year. Serum levels of KL-6, SP-D and TGF-β1 were measured and their associations with disease severity and progression were analysed. KL-6, SP-D and TGF-β1 levels were significantly higher in IPAF and CTD-ILD patients compared to CTD without ILD (