ACVRL1 and capillary malformation: One common form of familial AVM is Hereditary Hemorrhagic Telangiectasia, caused by autosomal dominant mutations in TGF-β/BMP-9 signaling pathway genes such as ENG, ACVRL1/ALK1, and SMAD4. Capillary malformation–arteriovenous malformation, another familial form of AVM is caused by mutations in EPHB4-RAS-ERK signaling pathway genes: RASA1 and EPHB4. One recent study systematically investigated the contribution of germline variants to bAVM and explore the critical molecular pathways underlying the pathogenesis of bAVM.