Dai et al. and others reported that Egln1 endothelial conditional knockout mice (Egln1EC−/−) can spontaneously develop PAH with severe pulmonary vascular remodeling and occlusive pulmonary vascular lesions even in normoxia conditions (61–63), whereas heterogenous Egln1EC+/− mice shows mild PAH symptoms (63). This evidence concerns the gene EGLN1 and pulmonary arterial hypertension.