Most of HHT cases are categorized into either HHT type 1 (HHT1) caused by mutations in endoglin (ENG), a TGF-ß type III auxiliary receptor mapped on chromosome 9 [1], or HHT type 2 (HHT2) caused by mutations in activin receptor-like kinase 1 (ACVRL1; ALK1), a TGF-ß type I serine-threonine kinase receptor located in chromosome 12 [3]. The gene discussed is ENG; the disease is hereditary hemorrhagic telangiectasia.