Combined with previous studies and PPHN, we reviewed and summarized the identified risk genes contributing to childhood-onset PAH with large amounts of literature evidence to date: BMPR2, TBX4, SOX17, SMAD9, KCNK3, CAV1, GDF2, ACVRL1, and ENG (Table1). This evidence concerns the gene SMAD9 and pulmonary arterial hypertension.