Immunohistochemical analysis of human lungs from patients with idiopathic PAH (IPAH) demonstrates increased OPG expression within pulmonary vascular lesions, and patients with IPAH also have increased serum levels of OPG, which correlate with prognostic markers and survival (Condliffe et al., 2012). Here, TNFRSF11B is linked to idiopathic pulmonary arterial hypertension.