Juvenile Polyposis Syndrome (JPS) is a hereditary condition in which people have a higher risk for benign (non-cancerous) polyps in the gastrointestinal (GI) tract, most commonly in the colon. Polyps can also be found in the stomach, small intestine, and rectum. “Juvenile” refers to the type of polyp that is seen in this condition. If these polyps are not removed, they can develop into cancer.
People who meet any of the following criteria are considered to have JPS:
- More than five juvenile polyps in the colorectum or
- Multiple juvenile polyps throughout the GI tract or
- Any number of juvenile polyps and a family history of juvenile polyposis
Most people with JPS will develop polyps by the age of 20. Some people only have a few polyps over the course of their life, but others may have more than 100 polyps.
JPS can be caused by changes in the genes BMPR1A and SMAD4. Genes carry information telling cells in the body how to work. Most people without JPS carry two working copies of the BMPR1A and SMAD4 genes in their cells. One copy of each gene is inherited from each parent. Cells from people with JPS carry one working copy of BMPR1A or SMAD4 and one copy of BMPR1A or SMAD4 that is changed. This change causes the gene to not work right. It is called a variant.
Variants in BMPR1A are found in about 28% of cases of JPS and variants in SMAD4 are found in about 27% of cases. For the remaining 45% of people with the condition who do not have variants in any of these genes, doctors do not yet know what other genes are related to JPS.
About a third (33%) of people with JPS have a parent who is also affected with the condition. About two-thirds (67%) of people with JPS do not have an affected parent or family history of polyps. In these cases, the change either happened in an egg or sperm cell when the child was formed or in one of the child’s cells during pregnancy. These children are the first in their families to have JPS. No matter how they acquired the BMPR1A or SMAD4 variant, people with JPS who are able to have biological children have a 50% (or 1 in 2) chance of passing it on to their children.
A doctor may suspect this diagnosis after looking at a person’s medical or family history. In most cases, a doctor or genetic counselor will ask questions about the person’s health and the health of other family members. Read more about genetic counseling and genetic testing.
Diagnosing this syndrome is usually done by sequencing the BMPR1A and SMAD4 genes to find variants (changes in genes).
Genetic testing does not always find a variant that is responsible for the syndrome. A person can still have the syndrome even if no variants in these genes are found. There are likely to be more undiscovered genes that play a role in the development of this syndrome.
While the polyps themselves are not cancerous, they can develop into cancer. The lifetime risk for GI cancers in people with JPS is thought to be 40-50%. People with JPS are also at an increased lifetime risk for stomach cancer (21% if multiple polyps are present), as well as small intestine and pancreatic cancers (rare but still increased risk).
Cancer screening involves tests to check for cancer before symptoms occur. The goal is to find cancer at the earliest and most treatable stage. Guidelines for cancer screening are available online. Recommended screenings may change over time as doctors learn more about this syndrome, so these screening tests should be discussed with a health care provider who knows this syndrome well.
Other ideas to reduce the risk of cancer include:
- Eat a healthful diet with lots of fruits and vegetables
- Get regular exercise
- Avoid smoking or using tobacco products
- Avoid secondhand smoke
- Avoid excess sun exposure and always wear sunscreen, hat, and protective clothing when out in the sun
- Get medical attention for unusual or ongoing symptoms
Due to a variant in SMAD4, some people with JPS have a combined syndrome called JPS and hereditary hemorrhagic telangiectasia (JPS/HHT). People with this condition can have juvenile polyps, nosebleeds, telangiectasias (widened thread-like tiny blood vessels near the surface of the skin), and arteriovenous malformations (abnormal connection between arteries and veins, sometimes in the brain or spine).
Because of the medical concerns related to this syndrome, specialists in the following areas may need to assess a child with JPS:
- Gastroenterology
- Otolaryngology (Ear, nose, and throat specialist)
- Pulmonology
- Cardiology
Resources for JPS:
- Peutz-Jeghers Syndrome and Juvenile Polyposis Syndrome Online Support Group (https://www.smartpatients.com/communities/peutz-jeghers-syndrome)
- National Organization for Rare Disorders – Juvenile Polyposis Syndrome (https://rarediseases.org/mondo-disease/juvenile-polyposis-syndrome/)
Other resources:
- Making Sense of Your Genes: A Guide to Genetic Counseling (ncbi.nlm.nih.gov/books/NBK115508/)
Adapted from educational materials developed by the St. Jude Children’s Research Hospital Cancer Predisposition Program