ACE and pulmonary fibrosis: The I/D of ACE gene can increase/decrease the activity of ACE in plasma and tissue.[15–18] ACE can not only act on pulmonary vascular endothelial cells, epithelial cells, fibroblasts, but also change pulmonary vascular tension and permeability, coagulation and fibrinolysis system, pulmonary fibrosis through renin angiotensin system, and affect the occurrence, prognosis and prognosis of IPF.