Two main types of HHT represent 80% of cases: HHT type 1 results from mutations in the encoding for the endoglin (ENG) gene, while HHT type 2 results from mutations in the activin type II-like receptor kinase 1 (ACVRL1) gene (encoding for the activin receptor-like kinase). Here, ACVRL1 is linked to hereditary hemorrhagic telangiectasia.