Moreover, OECs isolated from patients with hereditary haemorrhagic teleangiectasia (HHT) carrying mutations in TGF-β receptors ACVRL1 (ALK-1, activin receptor-like kinase 1) or ENG (endoglin) displayed abnormalities comparable to the vascular lesions observed in HHT patients [11]. Here, ACVRL1 is linked to hereditary hemorrhagic telangiectasia.