Up to know only one study of BMP9 response to novel activin receptor-like kinase 1 (ALK1) mutants derived from non synonymous SNPs in hereditary hemorrhagic telangiectasia type 2 (HHT2) patients has been reported [35] and no previous studies have assessed BMP9 variations. This evidence concerns the gene ACVRL1 and hereditary hemorrhagic telangiectasia.