Mutations in the BMPR2 gene are strongly associated with the development of familial PAH (FPAH) and idiopathic PAH (IPAH) (181, 182), and PAH patients with BMPR2 mutations typically have a younger onset, exhibit increased disease severity and elevated mPAP and pulmonary vascular resistance, have a poorer response to acute vasodilatory testing and are at greater risk of death (183). This evidence concerns the gene BMPR2 and idiopathic pulmonary arterial hypertension.