Previous studies have identified CHI3L1 as an indicator of disease severity and prognosis in patients with idiopathic PAH (21), PAH associated with scleroderma (22), and IPF (19), but the mechanism of CHI3L1 in the pathogenesis of PH has not been investigated to our knowledge. This evidence concerns the gene CHI3L1 and idiopathic pulmonary fibrosis.