These entities are often sporadic but are found in association with variants of the RASA1 and EPHB4 genes (capillary malformation–arteriovenous malformation, CMAVM; OMIM #608354) or ACVRL1, ENG, and SMAD4 genes (hereditary hemorrhagic telangiectasia, HHT; OMIM #187300). This evidence concerns the gene ACVRL1 and hereditary hemorrhagic telangiectasia.