Recently, it was shown that animal models of PAH [251,252], hypoxic pulmonary hypertension (HPH) [253] and human patients with PAH [199,206], including idiopathic pulmonary arterial hypertension (IPAH) [253], might have an increased ratio of ACE/ACE2. This evidence concerns the gene ACE2 and idiopathic pulmonary arterial hypertension.