uvenile polyposis (JP or JPS for juvenile polyposis syndrome) is an autosomal dominant disorder that often presents in childhood. It is characterized by the presence of hamartomatous (juvenile) polyps that vary in number from fi ve to several hundred (1, 2). Th e polyps are found primarily in the colorectum, but they can be present throughout the gastrointestinal tract, from the stomach to the rectum (2). Even though these polyps are normally benign, patients have an increased risk of gastrointestinal cancer (1-3). Th is disease occurs in approximately 1 in 100,000 people (4), and in 50% to 60% of the patients a germline mutation in SMAD4 (5) or bone morphogenic protein receptor 1A (BMPR1A) (6) genes can be found. Hereditary hemorrhagic telangiectasia (HHT; Osler-Weber-Rendu syndrome) is another autosomal dominant disorder distinguished by vascular dysplasia in multiple organs that can result in excessive bleeding. Th is syndrome was initially described by Osler in 1901 in a report of a familial form of recurrent mucous membrane bleeding from telangiectasias (3). Characteristic features include telangiectasias of the skin and oral and nasal mucosa, epistaxis, and arteriovenous malformations (AVMs) of the lungs, liver, brain, and gastrointestinal tract that can lead to hemorrhage and stroke (7-9). Th e frequency of this syndrome diff ers between populations, but it ranges from 1 in every 1300 Afro-Caribbeans in the Netherlands Antilles (10) to 1 in every 40,000 people in northern England (4). Approximately 80% of the families have a mutation in the endoglin (ENG) (5) or activin receptor-like kinase 1 (ALK1) (6) genes, while the remaining 20% of patients have a mutation in the SMAD4 gene (7) or in new loci mapped to chromosome 5 and chromosome 7 (8). A syndrome that combines JP and HHT was fi rst described in 1980 (9, 10). Th ese patients exhibit symptoms of both