Mutations in the SMAD4 gene (chromosomal locus 18q21.2) were also found in HHT patients, although more rarely than ENG and ACVRL1 mutations, resulting in a combined syndrome of HHT and juvenile polyposis (JP-HHT; OMIM 175050) (4, 6). This evidence concerns the gene ACVRL1 and hereditary hemorrhagic telangiectasia.