 These usually begin appearing before age 20, but the term "juvenile" refers to the type of polyp (i.e benign hamartoma, as opposed to adenoma for example), not to the age of the affected person.While the majority of the polyps found in juvenile polyposis syndrome are non-neoplastic, hamartomatous, self-limiting and benign, there is an increased risk of adenocarcinoma.Solitary juvenile polyps most commonly occur in the rectum and present with rectal bleeding.