Juvenile Polyposis Syndrome

Types of juvenile polyposis syndrome

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)
• Arteriovenous malformations (abnormal connection between arteries and veins, sometimes in the brain or spine)
  

Cancer risk with juvenile polyposis syndrome

While JPS polyps are not cancerous, they can develop into cancer. The lifetime risk for gastrointestinal cancers in those with JPS is 40–50% (1 in 2). People with JPS are also at an increased lifetime risk for stomach cancer, small intestine cancers, and pancreatic cancers.

Signs of juvenile polyposis syndrome

Signs of JPS include any of the following:

• More than 5 juvenile polyps in the colorectum
• Multiple juvenile polyps through the GI tract
• Any juvenile polyps and a family history of juvenile polyposis

Most people with JPS will develop 5 polyps by age 20. Some people only have a few polyps over the course of their life. Others may have more than 100 polyps.

Causes of juvenile polyposis syndrome

Genes carry information telling cells in the body how to function. JPS is caused by changes in the genes BMPR1A or SMAD4. Most people with changes in the SMAD4 gene have JPS/HHT. A gene change that causes the gene to not work right is called a mutation.

Mutations in BMPR1A are found in about 28% of people with JPS. Mutations in SMAD4 are found in about 27% of people with JPS. We do not yet know what causes JPS in the remaining 45% of people with this condition.

How juvenile polyposis syndrome is inherited

Most people without JPS carry 2 working copies of the BMPR1A and SMAD4 genes in their cells. They inherit 1 copy from their mother and 1 copy from their father.

Cells from people with JPS carry 1 working copy of BMPR1A or SMAD4 and 1 mutated copy of BMPR1A or SMAD4. This mutated copy causes the gene to not work right.

About 33% of people (1 out of 3) with JPS whose condition is caused by BMPR1A or SMAD4 mutations have a parent who also has the condition. For the remaining 66% people (2 out of 3), the mutation in BMPR1A or SMAD4 either happened in an egg or sperm or in 1 of the person’s cells during pregnancy. These people are the first in their families to have JPS caused by BMPR1A or SMAD4 mutations.

People with JPS whose condition is caused by BMPR1A or SMAD4 mutations and are able to have biological children have a 50% (1 in 2) chance of passing the change in the BMPR1A or SMAD4 gene on to their children. Children who inherit the change in BMPR1A or SMAD4 will have JPS.

Juvenile polyposis syndrome diagnosis

Health history

A health care provider may suspect that your child has JPS after studying their medical and family cancer history.

This information helps the health care provider and the genetic counselor know if:

• There are more cancers than normal in your family
• These cancers happened at a younger age than expected
• The cancers are those that are seen in juvenile polyposis syndrome

Your provider or genetics counselor may recommend BMPR1A or SMAD4 genetic testing if they suspect JPS. Learn more about types of genetic tests.

Genetic testing for juvenile polyposis syndrome

A blood sample is sent to a genetic testing lab. The lab runs genetic tests that looks for changes in the BMPR1A or SMAD4 genes.

If your child has a BMPR1A or SMAD4 mutation, the genetic counselor will work with your family to:

• Find out if other family members should consider testing for a BMPR1A or SMAD4 mutation
• Help your family understand the increased cancer risk from JPS
• Give you information to help with your decisions about prenatal genetic testing

Genetic testing before or during pregnancy

Parents may choose to do prenatal testing to find out if a pregnancy is affected with a known BMPR1A or SMAD4 mutation. Testing may take place either before pregnancy occurs or during pregnancy.

You should work with a genetic counselor to review the pros and cons of the test. The genetic counselor can also help you prepare for the test results.

Testing before pregnancy is called preimplantation genetic testing (PGT). This special type of genetic testing is done along with in vitro fertilization (IVF). PGT tests embryos for a known BMPR1A or SMAD4 mutation before a provider places the embryo into the uterus.

Testing during pregnancy can help providers see if a pregnancy has a known BMPR1A or SMAD4 mutation. A doctor gathers cells from the pregnancy in 1 of 2 ways:

• Chorionic villus sampling (CVS) is done during the first 3 months of pregnancy (1st trimester).
• Amniocentesis is done after the first 3 months of pregnancy (2nd trimester or later).

After tissue collection, the lab checks the sample for the BMPR1A or SMAD4 mutation. Both tests carry minor risks. Discuss these risks with an experienced health care provider or a genetic counselor.

Special concerns for genetic testing

Take time to think carefully about the benefits and risks of genetic testing. Speak with a genetic counselor before testing. If you decide to get tested, talk with your health care provider or a genetic counselor about your results so you can understand what they mean.

Sometimes, children or adults with JPS feel sad, anxious, or angry after getting their test results. Parents may feel guilty if they pass the BMPR1A or SMAD4 gene mutation to 1 or more of their children. People with a BMPR1A or SMAD4 gene mutation may also have trouble getting disability or life insurance.

Read more about genetic discrimination.

Monitoring and follow-up care for juvenile polyposis syndrome

People of any age with JPS or JPS/HHT have a higher risk of cancer. Monitor your child’s health and help them adopt healthy habits. Continue to have regular physical checkups and screenings. That way, the care team can find any polyp or cancer early at the most treatable stage.

Cancer screening for those with juvenile polyposis syndrome

In general, treatment of JPS involves routine screening to detect juvenile polyps. The goal is to find and remove polyps at the earliest and most treatable stage.

Screening tests may include:

• Yearly exam should be done by a health care provider familiar with JPS.
• Monitor for rectal bleeding, anemia, abdominal (belly) pain, constipation, diarrhea, or changes in the stool. If your child has these symptoms, contact your care team right away.
• Complete blood count should begin in the mid-teen years to monitor for anemia.
• Colonoscopy and upper endoscopy should begin in the mid-teen years or when symptoms start.
  • If negative, screening should be repeated every 3 years or as suggested by a health care provider.
  • If only 1 or a few polyps are found, they are removed. Screening is then done yearly or as suggested by the care team.
  • If many polyps are found, your child may need part or most of their colon or stomach removed.
• Blood tests should be done with treatment for iron deficiency.
• Lung exams should be done about every 5 years using contrast echocardiogram.
• An MRI exam of the brain should be done during childhood and again after puberty if the first childhood MRI was normal.

Because of the complex care that people with JPS/HHT need, seek treatment at a Hereditary Hemorrhagic Telangiectasia Treatment Center.

Living with juvenile polyposis syndrome

Problems to watch for

Watch closely for signs or symptoms that could signal polyps or cancer, such as:

• Unexplained weight loss
• Loss of appetite
• Pain in the abdomen (belly)
• Blood in the stool or changes in bowel habits
• Aches, pains, lumps, or swelling that have no clear cause
• Headaches or changes in vision or nerve function that do not go away

Seek medical help if anything unusual appears.

Maintain a healthy lifestyle

Habits that will help you maintain a healthy lifestyle include:

• Eat a healthy diet with fruits and vegetables.
• Get regular exercise.
• Avoid smoking or using tobacco products.
• Avoid secondhand smoke.
• Avoid excess sun exposure. Always wear sunscreen, a hat, and protective clothing when out in the sun.

Juvenile polyposis syndrome care at St. Jude

The St. Jude Cancer Predisposition Program is dedicated to diagnosing and screening children with a genetic predisposition for cancer. Our program offers the best clinical care possible. We engage in cutting-edge research to gain more information about genetic disorders and cancer, and to improve the care and treatment for patients who are affected by these conditions. Learn more about the Division of Cancer Predisposition at St. Jude.

Our genetic counselors, clinicians, genetics nurse practitioners, and research assistants work together to provide patients with:

• A complete health history
• A record of cancer that happened over the past 3 generations (family tree or pedigree) to see how diseases were passed down
• Physical exams to check for genetic disease
• Confidential genetic counseling and testing
• Cancer screenings for those with genetic disease to detect and treat cancer as soon as it occurs
• Recommended cancer treatments and ways to reduce cancer risk
• Genetic testing for immediate (1^st degree) relatives

JPS increases your child’s risk for cancer. 

If you have questions about the Genetic Predisposition Clinic and care for Juvenile Polyposis Syndrome, email our team at GPTeam@stjude.org.