Objective: We aimed to examine whether heparin-binding epidermal growth factor-like growth factor (HB-EGF) affects the lung fibrosis process through the activation of p38 protein in mitogen-activated protein kinases (MAPK) signaling pathway, as well as the expression of downstream inflammatory factors. Methods: The expression levels of HB-EGF, collagen type I (COL-I), and hexokinase 2 (HK2) in peripheral blood mononuclear cells (PBMCs) of patients with connective tissue disease-related interstitial lung disease (CTD-ILD) were examined by qPCR, Western blotting and ELISA. Results: In vitro experiments showed that HB-EGF was increased in almost all subtypes [rheumatoid arthritis (RA), systemic sclerosis (SSc) and idiopathic inflammatory myopathies (IIMs)] as well as in all groups (P