Loss of function ENG mutations leads to hereditaryhemorrhagic telangiectasia (HHT) type 1, an autosomal dominant syndromecharacterized by vascular dysplasia associated with PAH.29 Relatively frequent mutations in the ENG gene associatedwith PAH have been described, although the role of these in disease is uncertain.18 However, in PAH, ENG expression has been reported aselevated on IPAH ECs, consistent with our scRNA-seq observation.30 In distinction from HHT patients in whom deficient ENG isassociated with PAH, in mice ENG deficiency is protective forhypoxic pulmonary hypertension. This evidence concerns the gene ENG and pulmonary arterial hypertension.