ACVRL1 and hereditary hemorrhagic telangiectasia: Inherited forms of familial AVM include hereditary hemorrhagic telangiectasia (HHT; most commonly due to mutations in ENG, ACVRL1/ALK1 or SMAD4) and capillary malformation—arteriovenous malformation syndromes (CM-AVM; usually due to RASA1 or EPHB4) and these have been shown to predispose to either multifocal or recurrent AVMs [11].