Less frequent HHT-causing mutations are detected in the MADH4/SMAD4 gene, resulting in a joint condition known as Juvenile Polyposis and HHT (JPHT) [8], where, in addition to HHT symptoms, colon polyps and thoracic aneurysms appear [9]. This evidence concerns the gene SMAD4 and juvenile polyposis/hereditary hemorrhagic telangiectasia syndrome.