1. Home
  2. Cancer genetics
  3. Consumer information

Facts for people and families with Juvenile Polyposis syndrome

This fact sheet contains general information about Juvenile Polyposis syndrome (JPS). Each person should see a genetic service for further information and advice.

Key Points

  • People with JPS have an increased chance of developing multiple polyps in the bowel and stomach. If these are left untreated, bowel (colorectal) or stomach cancer can develop.
  • People with JPS due to a faulty SMAD4 gene may also have a condition known as Hereditary Haemorrhagic Telangiectasia (HHT).
  • Family members (including children) can be referred to a genetic service where experts can provide information, advice and support about their chance of developing cancer and the option of genetic testing.
On this page
Expand all Collapse all Back to top

Juvenile Polyposis syndrome is a genetic condition that leads to ‘juvenile’ type polyps in the bowel and stomach. It can be due to faults (mutations) in the SMAD4 or BMPR1A genes but sometimes the genetic cause is not known. SMAD4 and BMPR1A are genes that help to control cell growth in the lining of the bowel and stomach.

Everyone has two SMAD4 genes and two BMPR1A genes (one from their mother, and one from their father). If one of these genes is not working this is known as having a faulty SMAD4 gene or a faulty BMPR1A gene, or having a SMAD4 mutation or a BMPR1A mutation. 

People with a faulty SMAD4 gene may also have a condition known as Hereditary Haemorrhagic Telangiectasia (HHT).

Cancer:

  • People with JPS have a 30-40% chance of developing bowel cancer and about a 20% chance of developing upper gastrointestinal cancer (usually stomach cancer) over their lifetime.
  • Not everyone with JPS will develop cancer.

Other features:

  • About 30% of people with a faulty SMAD4 gene also have a condition called Hereditary Haemorrhagic Telangiectasia (HHT). This can lead to abnormal connections between arteries and veins (arteriovenous malformations (AVMs)).

Bowel polyps and cancer:

  • To find bowel polyps and cancer early, people with JPS should have bowel cancer screening every 2 years from age 15 years. This involves having a colonoscopy. If polyps are found on colonoscopy, bowel screening should be done every year.
  • To find upper gastrointestinal / stomach cancer early, people with JPS should have screening every 2 years starting from age 25-30 years. This involves having a gastroscopy. If polyps are found on gastroscopy, screening should be done every year.

Other features:

  • People with a faulty SMAD4 gene should see a specialist doctor experienced in managing HHT.

Family members (including children) of someone with a faulty SMAD4 or BMPR1A gene can have genetic testing to check who has the faulty gene and who does not. Their doctor can refer them to a genetic service to find out more about their chance of developing cancer and what genetic testing involves.

If a person does have a faulty SMAD4 or BMPR1A gene: 

  • they can pass it on to their children
  • each child has a 50% (1 in 2) chance of being born with it. Pregnancy planning options are available to people who want to prevent the faulty gene being passed on.

If a person does not have a faulty SMAD4 or BMPR1A gene:

  • they have the same chance of developing cancer as the general population (unless there are other factors that increase this risk)
  • they cannot pass it on to their children.

People who decide not to have genetic testing should still get advice about managing their chance of developing cancer.

Version 3

Date Summary of changes
28/06/2022

Consumer information sheet reviewed in line with risk management protocol (ID 751). Approved for publication with the following changes made: 

  • What is the risk of cancer and other features of JPS?:
    • 'About 20% of people with a faulty SMAD4 gene also have a condition called Hereditary Haemorrhagic Telangiectasia (HHT).' changed to 'About 30% of people...'
  • How can this increased risk of polyps, cancer and other features of JPS be managed?
    • Upper gastrointestinal/stomach cancer: '...screening every 2 years from age 25 years.' changed to '...screening every 2 years starting from age 25-30 years'

Version updated to V.3. To be reviewed alongside ID 751 when next due for review.

Version 2

Date Summary of changes
10/12/2019

Document reviewed in line with ID 751 following May 2019 reference committee meeting. Approved for publication with the following changes made: 

  • Key points: removed "JPS is caused by faults (mutations) in the SMAD4 or BMPR1A gene."
  • What is Juvenile Polyposis syndrome? section:
    • Section heading changed from "What is a faulty SMAD4 gene or a faulty BMPR1A gene?" to "What is Juvenile Polyposis syndrome?"
    • First paragraph added
    • Minor wording changes 
  • What is the risk of cancer and other features of JPS? section:
    • Other features: added "This can lead to abnormal connections between arteries and veins (arteriovenous malformations (AVMs))."
  • More information and support section:
    • Added Cure HHT website

Version updated to V.2. To be reviewed again alongside protocol ID 751 when next due for review.

Version 1

Date Summary of changes
27/04/2018 Developed in conjunction with consumer information sheet working group and presented at the November 2017 Cancer Genetics meeting. Discussions continued over email and document approved for publication. V.1. 
11/06/2019 What is the risk of cancer and other features of JPS section: 'about a 30-40% chance' changed to 'a 30-40% chance'

This cancer genetics fact sheet is a guide only and cannot cover every possible situation. The information provided is not intended to replace discussion with a health professional, and should not be interpreted as medical advice. While eviQ endeavours to link to reliable sources that provide accurate information, eviQ and the Cancer Institute NSW do not endorse or accept responsibility for the accuracy, currency, reliability or correctness of the content of linked external information sources. Use of this document is subject to eviQ's disclaimer available at www.eviQ.org.au/copyright  

Send feedback for this page

First approved:
Last reviewed:
Review due:

The currency of this information is guaranteed only up until the date of printing, for any updates please check:

https://www.eviq.org.au/p/3439

13 Oct 2024