Peutz-Jeghers syndrome

Diagnosis and Testing

How do I get tested for Peutz-Jeghers syndrome?

Peutz-Jeghers syndrome can be confirmed by genetic testing. A genetic test looks for changes in your DNA that cause areas of your body to not work properly. A small tube of blood or a saliva sample is collected and sent to a specialized laboratory for testing.

Genetic testing for Peutz-Jeghers syndrome has to be ordered by a medical professional, such as a doctor or a genetic counselor, after a visit to the medical clinic. Visit the National Society of Genetic Counselors website to learn more about genetic counseling services and to find a genetic counselor in your area.

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How old do you have to be to get tested for Peutz-Jeghers syndrome?

Is there more than one test for Peutz-Jeghers syndrome?

Who else in my family should be tested for Peutz-Jeghers syndrome?

Is there prenatal testing for Peutz-Jeghers syndrome?

What information can I get from genetic testing for Peutz-Jeghers syndrome?

What does it mean to have a clinical diagnosis of Peutz-Jeghers syndrome?

How is a clinical diagnosis of Peutz-Jeghers made?

Do all mutations in the [i]STK11[/i] gene carry the same risks in Peutz-Jeghers syndrome?

How old do you have to be to get tested for Peutz-Jeghers syndrome?

Genetic testing for Peutz-Jeghers syndrome usually happens after a person develops symptoms and is seen by a medical professional. Symptoms can show up anytime between childhood and adulthood, so people can be tested at any point in their lifetime. Once a person is found to have a genetic mutation, family members can also be tested for the mutation to see if they also have Peutz-Jeghers syndrome. Family members of a person with a known genetic mutation can be tested even before they have symptoms. This includes children and unborn babies.

Is there more than one test for Peutz-Jeghers syndrome?

Genetic analysis of the STK11 gene can be completed through several different types of test to confirm Peutz-Jeghers syndrome (PJS).

If there is a known gene mutation in a family, targeted testing, also known as single site testing, can be ordered. With targeted testing, the laboratory will only look for one specific genetic change instead of scanning the entire gene. This is generally the least expensive option offered by testing companies. In order to have targeted testing, the doctor must provide a copy of the patient's relative's positive genetic test result so the laboratory knows what genetic change to test.

There are also testing options when a gene mutation has not been identified in the family. Many laboratories offer complete analysis of the STK11 gene. This analysis involves sequencing and deletion/duplication analysis of the STK11 gene.

There are numerous genes beyond STK11 gene that can be associated with hereditary cancer. In some situations, testing for multiple genes may be more efficient and/or cost-effective. This type of testing is often referred to as multi-gene testing or panel testing. Cancer panels often include PJS, and other genes that are associated with hereditary cancer.

Consultation with a medical geneticist or genetic counselor is recommended before genetic testing so that all of the options and possible test results can be discussed ahead of time. This individual will also help explain the test results and coordinate any follow-up as needed.

Visit the National Society of Genetic Counselors website to learn more about genetic counseling services and to find a genetic counselor in your area.

References
Who else in my family should be tested for Peutz-Jeghers syndrome?

Blood relatives of a person with Peutz-Jeghers syndrome (PJS) are all at risk to also have PJS. All first-degree relatives (parents, children, brothers, and sisters) of a person with a genetic mutation in the STK11 gene have a 50% risk to also have the mutation and have PJS. These individuals should consider being tested to see if they also carry the mutation. Early diagnosis can help reduce the chances of serious complications from the condition.

Consultation with a medical geneticist or genetic counselor is recommended before genetic testing so that all of the options and possible test results can be discussed ahead of time. This individual will also help explain the test results and coordinate any follow-up as needed.

Visit the National Society of Genetic Counselors website to learn more about genetic counseling services and to find a genetic counselor in your area.

References
Is there prenatal testing for Peutz-Jeghers syndrome?

Testing for Peutz-Jeghers syndrome is not part of routine prenatal screening or testing. The symptoms of Peutz-Jeghers syndrome also would not show up on a prenatal ultrasound. However, prenatal testing for Peutz-Jeghers syndrome can be done on an unborn baby (fetus) if there is already a known mutation in a parent or sibling of the fetus through a specialized procedure to get a sample of the placenta (chorionic villus sampling, or "CVS") or amniotic fluid (amniocentesis). The risks and benefits of prenatal testing for Peutz-Jeghers syndrome should be discussed with a genetic counselor. Visit the National Society of Genetic Counselors website to learn more about genetic counseling services and to find a genetic counselor in your area.

References
What information can I get from genetic testing for Peutz-Jeghers syndrome?

Genetic testing for Peutz-Jeghers syndrome (PJS) includes looking for changes in the sequence of the DNA, specifically in the STK11 gene. Changes that causes the STK11 gene to not work properly are called pathogenic variants or mutations.

If an individual with PJS or family member is found to have a pathogenic variant or mutation in the STK11 gene, this means the diagnosis of PJS is confirmed.

If an individual with a known pathogenic variant or mutation in the STK11 gene is found not to have that chance, it is very unlikely they have PJS.

However, about 5% of people who have all of the symptoms of PJS do not have a pathogenic variant or mutation in the STK11 gene and that does not take away the diagnosis of PJS from them. Those individuals are still treated medically as if they have PJS.

If an individual with no signs of PJS and no family history of PJS has genetic testing that finds no changes in a STK11 gene, this means it is unlikely that they have PJS.

Another type of DNA change that may be found in genetic testing is called a variant of uncertain significance (VUS). This means that there was a change in the DNA making up the STK11 gene, but it is uncertain whether or not this change has an impact on the way the gene works. If you are found to have a VUS, additional testing may be available to you and/or your family members to try to find out whether or not the change is actually impacting the gene.

Consultation with a medical geneticist or genetic counselor is recommended before genetic testing so that all of the options and possible test results can be discussed ahead of time. This individual will also help explain the test results and coordinate any follow-up as needed.

Visit the National Society of Genetic Counselors website to learn more about genetic counseling services and to find a genetic counselor in your area.

What does it mean to have a clinical diagnosis of Peutz-Jeghers syndrome?

A clinical diagnosis of Peutz-Jeghers syndrome (PJS) means that a person has enough physical symptoms of PJS that they can be treated as if they have the condition, even if they have not had genetic testing. In 5% of people with a clinical diagnosis of PJS, their genetic testing will not find a disease-causing change. However, they are still considered to have PJS and should be managed the same way as a person with genetically-confirmed PJS.

According to one clinical guideline, the diagnosis of PJS is established in a person with one of the following:

  • Two or more histologically confirmed PJS-type hamartomatous polyps
  • Any number of PJS-type polyps detected in one individual who has a family history of PJS in at least one close relative
  • Characteristic mucocutaneous pigmentation in an individual who has a family history of PJS in at least one close relative
  • Any number of PJS-type polyps in an individual who also has characteristic mucocutaneous pigmentation
References
How is a clinical diagnosis of Peutz-Jeghers made?

To have a clinical diagnosis of Peutz-Jeghers syndrome (PJS), a person must have at least one of the following:

  • Two or more PJS-type hamartomatous polyps (confirmed by histology)
  • Any number of PJS-type polyps and a family history of PJS
  • Mucocutaneous macules and a family history of PJS
  • Any number of PJS-type polyps and mucocutaneous macules
Do all mutations in the [i]STK11[/i] gene carry the same risks in Peutz-Jeghers syndrome?

It is unclear whether different types of mutations in the STK11 gene cause different risks in Peutz-Jeghers syndrome. Different types of mutations may include a change in the DNA that is like a typo, where one letter is substituted for another (missense mutation) or a change due to a missing portion of DNA (deletion). In one study, age of onset of GI symptoms was noted to be earlier in individuals with a deletion than those with missense mutations. In another study, cancer risks were not found to differ based on mutation type.

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