GDF2 and heritable pulmonary arterial hypertension: Mutations in other genes, mostly related to BMPR2 signaling, have been described in a small additional percentage of patients with familial HPAH, including SMAD9, ACVRL1, ENG, CAV1, and KCNK36 and more recently in ATP13A3, SOX17, GDF2 (BMP9) and AQP17.