Signaling mediated by bone morphogenic protein receptor 2 (BMPR2), a member of the TGF-β superfamily, has been shown to play a key role in familial pulmonary hypertension, and mutations in the gene encoding this receptor have also been found in 15–40% of idiopathic cases of PAH (37, 38). Here, BMPR2 is linked to pulmonary arterial hypertension.