The bone morphogenetic protein receptor 2 (BMPR2) signaling pathway has become a key focus of investigation since BMPR2 gene mutations were identified as the main predisposing risk factor in the heritable forms of PAH (HPAH) (72), with dysfunction in the signaling pathway present in all subtypes of PAH (73). The gene discussed is BMPR2; the disease is heritable pulmonary arterial hypertension.