Genetic diagnosis is based on the identification of a mutation in the transforming growth factor-beta (TGF-β) signaling pathway genes: Endoglin (ENG), activin receptor-like kinase 1 (ACVRL 1), or SMAD4 characterized by the juvenile polyposis syndrome (JPS) usually associated with HHT [2,3]. The gene discussed is ENG; the disease is hereditary hemorrhagic telangiectasia.