Also down‐regulated are ACVRL1—mutations in which cause vessel malformations in hereditary haemorrhagic telangiectasia 46—endothelin 1 (EDN1), which encodes vasoconstrictive peptides, and CCL2, which has chemotactic activity for monocytes and basophils. This evidence concerns the gene CCL2 and hereditary hemorrhagic telangiectasia.