The bone morphogenetic protein (BMPs) signaling pathway is another important pathway implicated in the PAH pathogenesis BMPs belong to the transforming growth factor-β (TGF-β) family, which consists of cytokines secreted by epithelial cells and fibroblasts (64) BMPs are essential in regulating growth, differentiation, and apoptosis in various cell types, including pulmonary vascular endothelium and fibroblasts (65). This evidence concerns the gene CLN5 and pulmonary arterial hypertension.