juvenile polyposis of infancy (Monarch Disease Ontology identifier MONDO_0019190) (JPI) is the most severe form of juvenile gastrointestinal polyposis and is characterized by pancolonic hamartomatous polyposis from stomach to rectum, diagnosed in the first two years of life. Also known as: infantile juvenile polyposis syndrome, infantile onset juvenile polyposis syndrome, juvenile polyposis syndrome of infancy.