In addition, the levels of circulating CHIT1 activity were increased in the patients with progressive SSc-ILD compared with stable SSc-ILD (Fig 7C), and overall progression-free survival was decreased in patients with increased levels of CHIT1 activity in a manner that persisted even after adjustment for the relevant covariates of age, gender, race, and smoking status (Fig 7D). Here, CHIT1 is linked to interstitial lung disease.