ACVRL1 and arteriovenous hemangioma/malformation: Additionally, mutations in BMP9 or the genes encoding BMP‐9/‐10 receptors, ACVRL1 (encoding ALK1) and ENG (encoding endoglin), lead to hereditary hemorrhagic telangiectasia (HHT), a rare genetic disease that is characterized by arteriovenous malformations (AVMs) and internal bleeding.34, 35, 36