Multiple polyposis syndromes, characterized by multiple colorectal polyps, are a group of diseases encompassing Familial adenomatous polyposis (FAP), Peutz-Jeghers syndrome (PJS), Juvenile polyposis syndrome (JPS), PTEN hamartoma tumor syndrome (PHTS), MUTYH-associated polyposis (MAP), NTHL1-associated polyposis (NAP), Polymerase proofreading-associated polyposis (PPAP), and MBD4-associated polyposis. The gene discussed is MBD4; the disease is juvenile polyposis syndrome.