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. Here, BMPR2 is linked to heritable pulmonary arterial hypertension.