Serrated polyposis syndrome (SPS) is a familial polyposis syndrome without a known genetic cause. It is diagnosed by the World Health Organization criteria of (1) five or more serrated polyps proximal to the sigmoid colon, two or more of which are 10 mm in diameter or greater, (2) any number of serrated polyps proximal to the sigmoid colon in an individual with a first-degree relative who has SPS, or (3) more than 20 serrated polyps distributed throughout the colon.