This information explains how having a mutation in the SMAD4 gene may affect you and your family.
In this resource, the word “family” means people related to you by blood. They’re not related to you through marriage or adoption. We also call these family members your blood relatives.
Your SMAD4 gene normally helps prevent cancers. A mutation in this gene causes it to stop working like it should.
It is important to understand that having a mutation in this gene does not mean you will definitely develop cancer. It means that you have an increased risk of developing certain types of cancers. The type of cancer can vary among people who have mutations in this gene, even within the same family.
What is my cancer risk if I have a SMAD4 mutation?
If you have a mutation in the SMAD4 gene, this means you have a condition called Juvenile Polyposis syndrome (JPS). JPS increases your risk of developing polyps (growths of tissue) in your colon or rectum. These polyps can lead to an increased risk for colorectal (colon and rectal) cancer. JPS also increases your risk for certain other types of cancers, including stomach cancer. JPS may increase your risk for small intestine (small bowel) and pancreatic cancer, but this is less common.
As we learn more about these mutations, we may learn they increase the risk for other types of cancers. Your genetic counselor will give you more information about your cancer risk if you have a mutation.
To learn more, read Hereditary Colon Cancer and Polyposis.
What can I do about my cancer risk if I have a SMAD4 mutation?
Your genetic counselor will review your results. They will talk with you about what cancer your mutation is linked to. As we research these mutations, we may learn they raise the risk for other types of cancers.
Your genetic counselor will also review your personal and family history of cancer and give you cancer screening recommendations. They may recommend you start having cancer screenings at a younger age or have them more often than most people. They may also suggest you get specialized screenings to help find cancer as early as possible.
Some examples of these cancer screenings include:
- Colonoscopies starting at an earlier age and more often than most people.
- An upper endoscopy (a procedure that lets your doctor see inside your stomach and small intestine).
If you’re having surgery for colon cancer or polyps, your genetic counselor may recommend you have extra colon tissue removed to prevent colon cancer.
Your genetic counselor will also talk with you about whether there are any other screening or prevention options that may be right for you.
What does a SMAD4 mutation mean for my blood relatives?
If you have a mutation, your biological parents, siblings, and children each have a 50% chance of having the same mutation. Your distant family members may also be at risk for having the same mutation.
Males and females have an equal chance of passing down a mutation in their family. You only need to inherit a mutation from one parent to have an increased risk for cancer.
Your genetic counselor will review your family history and talk with you about whether they recommend genetic testing for your blood relatives.
What happens if I do not have a mutation?
If you do not have a mutation or if we find a variant of uncertain significance (VUS), your genetic counselor will review your personal and family history of cancer. They’ll talk with you about the general cancer screening guidelines you should follow.
A VUS is a change in a gene, but we don’t yet know if it is linked with a higher risk for cancer. Most VUS are eventually found to be normal changes that do not affect your health.