Approximately 20% of patients with IPAH carried mutations in bone morphogenetic protein receptor type 2 (BMPR2), where a loss of BMPR2 function may compromise the integrity of the endothelial barrier and contribute to endothelial dysfunction by mediating endothelium-derived nitric oxide bioactivity (2, 13, 14). The gene discussed is BMPR2; the disease is idiopathic pulmonary arterial hypertension.