What is juvenile polyposis syndrome?
Juvenile polyposis syndrome (JPS) is a hereditary condition that is characterized by the presence of hamartomatous polyps in the digestive tract. Hamartomas are noncancerous (benign) masses of normal tissue that build up in the intestines or other places. These masses are called polyps if they develop inside a body structure, such as the stomach or intestines. The term “juvenile polyposis” refers to the type of polyp (juvenile polyp) that is found after examination of the polyp under a microscope, not the age at which people are diagnosed with JPS.
Polyps may frequently develop in a person with JPS by age 20. The number of polyps a person has during his or her lifetime can range from around 5 to more than 100. Most juvenile polyps are noncancerous, but there is an increased risk of cancer of the digestive tract, such as stomach, small intestine, colon, and rectum cancers, in families with JPS.
JPS is suspected when a person’s symptoms and family history fit any of the following categories:
More than 5 juvenile polyps of the colon and/or rectum
Multiple juvenile polyps throughout the digestive tract
Any number of juvenile polyps and a family history of juvenile polyps
What causes JPS?
JPS is a genetic condition. This means that the risk for polyps and cancer can be passed from generation to generation in a family. Based on current research, 2 genes have been linked to JPS. They are called BMPR1A and SMAD4. A genetic alteration that disrupts the function of either the BMPR1A gene or the SMAD4 gene makes a person more likely to develop juvenile polyps and cancer of the digestive tract over his or her lifetime. This type of change to a gene can also be called a genetic mutation, gene alteration, pathogenic or likely pathogenic germline variant, or a disruptive gene change. Not all families that have JPS will have identifiable genetic alterations in BMPR1A or SMAD4. Other genes are being studied regarding their link to JPS.
How is JPS inherited?
Normally, every cell has 2 copies of each gene: 1 inherited from the mother and 1 inherited from the father. JPS follows an autosomal dominant inheritance pattern, in which an alteration in only 1 copy of the gene is sufficient to develop the condition. This means that a parent with this alteration may pass along a copy of their normal gene or a copy of the gene with the disruptive change. Therefore, a child who has a parent with this change has a 50% chance of inheriting the same disruptive gene change. A brother, sister, or parent of a person who has this alteration also has a 50% chance of having the same disruptive gene change. However, if the parents test negative for the genetic alteration (meaning each person’s test results found no disruptive gene change), the risk to the siblings significantly decreases but their risk may still be higher than an average risk.
Options exist for people interested in having a child when a prospective parent carries the genetic change that increases the risk for a hereditary cancer syndrome. Preimplantation genetic diagnosis (PGD) is a medical procedure done in conjunction with in-vitro fertilization (IVF). It allows people who carry a specific known disruptive gene change to reduce the likelihood that their children will inherit the condition. A woman’s eggs are removed and fertilized in a laboratory. When the embryos reach a certain size, 1 cell is removed and is tested for the hereditary condition in question. The parents can then choose to transfer embryos which do not have the disruptive gene change. PGD has been in use for over 2 decades and has been used for several hereditary cancer predisposition syndromes. However, this is a complex procedure with financial, physical, and emotional factors to consider before starting. For more information, talk with an assisted reproduction specialist at a fertility clinic.
How common is JPS?
It is estimated that between 1 in 16,000 and 1 in 100,000 people has JPS.
How is JPS diagnosed?
A diagnosis of JPS is made if a person’s symptoms and family history fits any of the 3 categories listed above. Blood tests are available for people who have JPS to look for disruptive changes in the BMPR1A gene or the SMAD4 gene. If an alteration is found, other family members may be diagnosed with JPS if they are tested and have the same gene mutation.
It is likely that there are other genes associated with JPS that have not yet been identified, so a blood test result that comes back as “negative”, meaning a gene change cannot be found, does not necessarily mean that a person does not have JPS. Therefore, meeting with a health professional who specializes in genetic diseases and conditions is recommended for people who have a family history or symptoms that suggests JPS.
What are the estimated cancer risks associated with JPS?
People with JPS are considered to be at an increased risk for colorectal, stomach, small intestine and pancreatic cancers. The overall estimated cancer risk associated with JPS is between 9% to 50%, but the risks for each specific type of cancer have not been determined.
What are other risks associated with JPS?
Individuals who carry a hereditary mutation in the gene SMAD4 are at risk for Hereditary Hemorrhagic Telangiectasia (HHT). Individuals with HHT often suffer from nosebleeds and are at risk for aneurysms and arteriovenous malformations (AVMs) in the brain and lungs.
What are the screening options for JPS?
It is important to discuss with your doctor the following screening options, as each person is different:
Any signs of rectal bleeding, anemia, abdominal pain, constipation, diarrhea, or other changes in the stool should be brought to the attention of a doctor and receive a medical evaluation.
Individuals who develop large numbers of polyps that cannot be removed during endoscopy may need to have surgery to remove part of the colon or stomach.
Individuals with JPS and a SMAD4 genetic mutation should talk to their doctor about additional screening for HHT, which may include a brain MRI, cardiac echocardiogram, and additional testing for lung AVMs.
Screening options may change over time as new technologies are developed and more is learned about JPS. It is important to talk with your doctor about appropriate screening tests.
Learn more about what to expect when having common tests, procedures, and scans.
Questions to ask the health care team
If you are concerned about your risk of colorectal cancer or other types of cancer, talk with your health care team. It can be helpful to bring someone along to your appointments to take notes. Consider asking the following questions:
What is my risk of developing cancer in the digestive tract?
How many colon polyps have I had in total?
What type of colon polyps have I had? The 2 most common types are hyperplastic polyps, which are noncancerous growths in the lining of the colon, and adenomatous polyps, which are growths in the lining of the colon that can become cancerous.
What can I do to reduce my risk of cancer?
What are my options for cancer screening?
If you are concerned about your family history and think your family may have JPS, consider asking the following questions:
Does my family history increase my risk for colorectal cancer or other types of cancer?
Does it suggest the need for a cancer risk assessment?
Will you refer me to a genetic counselor or other genetics specialist?
Should I consider genetic testing?
To find a genetic counselor in your area, ask your health care team or visit the following website: