Juvenile polyposis syndrome (JPS) is characterized by an increased number of hamartomatous polyps in the gastrointestinal tract (GI). They can occur in the stomach, small intestine, colon, and rectum.
Most individuals with JPS have some polyps by age 20 years. The number varies from persons to person, with some may have only four or five polyps and others having more than a hundred. If the polyps are left untreated, they may cause bleeding and anaemia. Most juvenile polyps are benign however, malignant transformation can occur.
Lifetime risk of cancer
Risk of GI cancer is much lower than in FAP or Lynch syndrome, and is thought to be between 10% to 50%. Most of this increased risk is attributed to colon cancer, but cancers of the stomach, upper GI tract, and pancreas can also occur.
JPS is diagnosed clinically if any one of the following is present:
- More than five juvenile polyps of the colorectum.
- Multiple juvenile polyps throughout the GI tract.
- Any number of juvenile polyps and a family history of juvenile polyps.
Juvenile polyps are hamartomas (normal tissue in abnormal location and proportions) and a distinctly different from adenomatous polyps. The genes known to be associated with JPS are BMPR1A and SMAD4. Approximately 20% of individuals with JPS have mutations in BMPR1A; approximately 20% have mutations in SMAD4. Molecular genetic testing of both genes is available on a clinical basis.
Routine gastroscopy and colonoscopy with endoscopic polypectomy to reduce the risk of bleeding, intestinal obstruction, and colon cancer. Total colectomy is sometimes needed when the number of polyps is large, or risk of cancer high. Gastroscopy and colonoscopy should start in the mid-teens (age 15 years) or earlier when symptoms occur.