Juvenile polyposis syndrome (JPS) is a genetically inherited condition that leads to the formation of numerous hamartomatous polyps throughout the gastrointestinal (GI) tract. JPS is rare, with an incidence between 1 in 100 000 and 1 in 160 000 individuals. It is autosomal dominant with incomplete penetrance and is due to mutations in SMAD4 or bone morphogenic protein type-1A (BMPR1A) in 60% of patients. Polyps begin forming prior to the age of 10 and can manifest as fewer than 5 to more than 100 polyps. Most are located in the colorectum (98%), but they can also be present in the stomach and the entire small intestine. JPS is not associated with malignancies beyond the GI tract.

Symptoms tend to present in the 20s and include bleeding, diarrhea, and intussusception. The average age at diagnosis is 18.5 years. There is a variant of JPS in infancy that carries similar presenting symptoms, with the addition of macrocephalus and hypotonia. Patients with JPS are at increased risk for colorectal cancer (CRC), with up to 20% developing it by age 35 and over 60% by age 60. JPS is associated with hereditary hemorrhagic telangiectasia (Osler-Weber-Rendu syndrome), especially if linked with mutation in SMAD4. The diagnosis of JPS is made if there are more than 5 juvenile polyps in the colorectum, multiple juvenile polyps in other areas of the GI tract, or with any number of juvenile polyps in someone with known family history.