What is juvenile polyposis syndrome (JPS)?
A syndrome is a group of features that often occur together. Juvenile polyposis syndrome (JPS) is a hereditary condition that makes some people likely to develop a certain type of polyp (tumor-like growth of tissue) in their gastrointestinal tract (stomach and intestines). People with JPS are more likely to develop certain types of cancers, including colorectal, stomach, upper gastrointestinal, and pancreatic cancer.
The polyps that people with JPS develop are called hamartomatous (ham-ar-tom-a-tus) juvenile-type polyps. The polyps grow mostly in the colon, stomach, and small intestine. They can sometimes cause gastrointestinal bleeding, obstruction, and abdominal pain. The word “juvenile” does not refer to the age of when the polyps start growing; it refers to what the cells and tissues look like under the microscope.
A small number of people with JPS also have a condition called hereditary hemorrhagic telangiectasia (HHT). People with HHT may have abnormalities in the development of blood vessels in certain organs that can cause bleeding issues, headaches, seizures, and other symptoms.Back to top
How is JPS diagnosed?
A diagnosis of JPS is made based on polyps or cancers that you have had, your family history, and genetic testing results. About 45% of people who are diagnosed with JPS have mutations in the SMAD4 and BMPR1A genes.Back to top
What does a positive SMAD4 or BMPR1A test result mean?
A positive test result means that a person has a disease-causing genetic mutation in the SMAD4 or BMPR1A genes. This means that a person has JPS and is believed to have an increased risk for developing hamartomatous juvenile-type polyps and certain cancers. Mutations in the SMAD4 gene can also sometimes be associated with the development of HHT.
It is important to understand that having JPS does not mean that a person will definitely develop cancer; it just means that they have an increased risk of developing certain cancers. Some people with SMAD4 or BMPR1A mutations may never develop cancer.Back to top
What does a “variant of uncertain significance” (or “ambiguous”) genetic test result mean?
Genes are written in letters called bases. We call the wrong spelling of a gene a “mutation” and a mutation can cause an increased risk of cancer. However, some spelling changes in genes do not cause disease. We are still learning which spellings are normal (harmless) and which may be disease-causing. Some individuals’ SMAD4 or BMPR1A genes may be spelled in a way that we can’t say whether it is normal or if it causes disease. These kinds of uncertain changes are called variants of uncertain significance.
If you have a variant of uncertain significance in the SMAD4 or BMPR1A genes, we may not be able to tell you if it is a normal change or a disease-causing change. In some situations, we may be able to test your relatives for the variant or we may be able to do lab tests, but we still may not be able to tell if the variant will increase your risk for polyps or cancer. If you have a variant, we will make recommendations for cancer screening based on your family history.Back to top
What does a negative SMAD4 or BMPR1A test result mean?
A negative test result means that no mutation was found in the SMAD4 or BMPR1A gene. This could happen if:
- You have a mutation in the SMAD4 or BMPR1A gene that cannot be detected with the testing method that was used. No one genetic testing method can find all mutations.
- You have a mutation in a different gene. Your genetic counselor may recommend testing for mutations in other genes that are also associated with hamartomatous (ham-ar-tom-a-tus) polyps and certain cancers.
- Your personal or family history of JPS-like features could be related to other factors, such as age, environment, and chance.
- There is a genetic mutation in your family, but you did not inherit it.
How should people with JPS manage their risks for cancer?
People with JPS have several options for managing their cancer risks. They can choose to undergo additional cancer screening exams or risk-reducing surgeries. The goal of screening is to detect cancer at early stages. Screening has not been proven to reduce cancer-related death in individuals with JPS, and current screening guidelines are based on expert opinion.
In families with diagnosed JPS, with or without an identifiable mutation, colonoscopy and upper GI endoscopic screening should begin in the mid-teens or at the time of initial symptoms (if earlier). Screening should be done every 3 years if no polyps are found. Once polyps are found, screening is recommended yearly or more often if directed by a doctor.
It is important to realize that screening does not prevent cancer. Current tests cannot always find cancers when they are early enough to be treated successfully.
Preventative surgery should be considered for people who have:
- Many polyps that cannot be managed by endoscopy
- Precancerous polyps
- Troublesome diarrhea and bleeding
- Significant family history of colorectal cancer
We recommend that all people with JPS be evaluated for HHT and managed appropriately based on their symptoms.Back to top
If I have an SMAD4 or BMPR1A mutation, what are the risks to my children?
If you have a mutation in the SMAD4 or BMPR1A gene, each of your children (or future children) has a 50% (1 in 2) chance of inheriting the mutation. A child who inherits the mutation will also inherit the associated risks. It is important to remember that inheriting the mutation does not mean that a person will definitely develop all the features of JPS.
You may want to consider genetic testing in children who are at risk of having an SMAD4 or BMPR1A mutation because they may be able to undergo certain cancer screenings. Your genetic counselor can help determine the risk for your children and other family members, and will also determine what would be an appropriate age for them to undergo genetic testing.Back to top
If I have an SMAD4 or BMPR1A mutation, what are my options for having children?
If you have an SMAD4 or BMPR1A mutation, you may want to learn about family planning options (starting a family or having more children). For example, embryos can be tested for the family’s genetic mutation before they are even implanted in a woman’s uterus. This process is called preimplantation genetic diagnosis (PGD). PGD is performed with in vitro fertilization (IVF) and may be an option for families who wish to have children without the mutation. To learn more, ask for a referral to a PGD-IVF specialist before attempting pregnancy.
Other possible family options include having children with the assistance of donor eggs or donor sperm or through adoption.Back to top
What if I have questions?
If you have any questions or concerns, please contact the MSK Clinical Genetics Service at 646-888-4050.Back to top