HHT can be classified into at least two types; type 1 (HHT1; OMIM 187300) is caused by mutations in Endoglin (ENG) gene and type 2 (HHT2; OMIM 600376) is caused by mutations in activin receptor-like kinase 1 (ACVRL1) gene [4], [10], [11]. This evidence concerns the gene ACVRL1 and hereditary hemorrhagic telangiectasia.