As shown in Table 1 and Fig. 4a, serum gremlin-1 concentrations were significantly higher in patients with IPF (mean concentration, 14.4 ng/mL; median, 11.5; interquartile range, 10.1–17.6), followed by those with non-IPF ILD (mean, 8.8 ng/mL; median, 9.1; interquartile range, 7.0–11.5) and healthy controls (mean, 1.6 ng/mL; median, 1.5; interquartile range, 1.2–1.9). Here, GREM1 is linked to idiopathic interstitial pneumonia.