CHIT1 and interstitial lung disease: These studies suggest that CHIT1/SMAD7 axis plays an important role in disease progression or exacerbation rather than initiator of fibrotic tissue response, and potential use of CHIT1/SMAD7 activity and expression both in serum and lung or BAL as a biomarker to predict disease severity and prognosis of patients with IPF and SSc-ILD.