BMPR2 and pulmonary arterial hypertension: Nevertheless, the discovery of a loss-of-function mutation in bone morphogenetic receptor II (BMPR2), a member of the TGF-β superfamily, in 20 to 30% of patients with idiopathic PAH (IPAH) and 60% of patients with familial PAH immediately paved the way for elucidating the pathobiology of the disease.6,7