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Testing the family after a PMS2 result | CION Cancer Clinics
Once a PMS2 fault is found, your parents, brothers, sisters and adult children each have a one in two chance of carrying it. They can be tested for that exact change, but PMS2 is tricky to test, so the laboratory must know precisely what to look for. This page covers who to test first, when children should test, and why cousin marriage matters. At CION Cancer Clinics, our oncologists explain what a gene result means for you and your family, and plan the checks that follow.
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Medically reviewed by Dr. Naresh GunduConsultant Medical Oncologist · MBBS, DNB (Internal Medicine), DM (Medical Oncology, AIIMS) · last reviewed September 2026, next review due September 2027
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On this page
- Who in the family should be tested for your PMS2 fault?
- Which relatives are offered the test, and when?
- How does testing a relative work?
- What do the words on the letter mean?
- What does a relative's result change for them?
- What this page cannot tell you
- Four things families say about testing for PMS2
- Common questions about testing the family for PMS2
The short answer
Who in the family should be tested for your PMS2 fault?
Your parents, brothers, sisters and adult children come first. Each has a one in two chance of carrying the same fault. They are tested for that exact fault only, and the laboratory must be told precisely which one it is.
Why PMS2 families often do not know
PMS2 carries the mildest risks of the Lynch syndrome genes. Many carrier families have little or no bowel cancer to point to. That is why a relative who feels safe because "nobody had it" may still carry the fault.
Why the laboratory matters more than usual
PMS2 has a near-identical copy elsewhere in our DNA. That copy does nothing, but it can confuse a laboratory test. Send your original report with each relative's sample, so the laboratory can use a method that checks the real gene.
What a relative gains
A carrier can start colonoscopy at the right time and catch growths early. A non-carrier can stop worrying and needs only the routine checks that anyone else would have. Either answer is useful, and the negative answer is the more common one in most families.
Who goes first if nobody else has been tested
If you are the first person in the family to test positive, start with your parents if they are alive and willing. If they are not, test your brothers and sisters next. A relative who has already had bowel or womb cancer should be near the front of the queue, whatever the branch.
A relative who tests negative for your family's fault does not need the extra colonoscopies that carriers are offered.Relative by relative
Which relatives are offered the test, and when?
Testing moves outwards through the family. The closest relatives go first because their chance of carrying the fault is highest.
Parents
Testing your parents shows which side the fault came from. That tells you whose brothers, sisters and cousins to contact next, and which side can be left alone. An older parent who has never had cancer can still carry a PMS2 fault.
Brothers and sisters
Each has an even chance of carrying it, whether male or female and whether or not they have had cancer. Men and women both need bowel checks if they carry it.
Adult children
Each child has a one in two chance. Bowel checks for PMS2 do not usually begin until the thirties, so there is no need to test teenagers.
A good time is often
- After they turn adult and can consent
- Before planning marriage or children
- Well before their first colonoscopy would be due
Relatives who have had cancer
An aunt with womb cancer or an uncle with bowel cancer is a priority. Their result can change their own follow-up and sometimes their treatment. It also helps confirm which branch of the family the fault runs through, which saves the other branch from needless worry.
Not sure whether this applies to you?
Ask an oncologistStep by step
How does testing a relative work?
You pass on the family letter
Your counsellor writes a letter naming the gene and the exact change. You share it with relatives yourself, by hand or on WhatsApp.
They have their own counselling
Each relative decides for themselves, after a session of their own. They talk through what either answer would mean, including for marriage and insurance.
The sample goes with your report
A blood or saliva sample is sent with a copy of your report. Using the laboratory that found your fault, or one experienced with PMS2, avoids a confusing result.
The result is explained in person
A carrier leaves with a plan for colonoscopy and, for women, womb awareness. A non-carrier leaves knowing this fault is not theirs to pass on.
On the family letter
What do the words on the letter mean?
- Familial variant
- The exact PMS2 change found in your family. Relatives are checked for this and nothing else.
- Cascade testing
- Testing that spreads out through the family, one branch at a time, starting with the closest relatives.
- Pseudogene
- A near-copy of PMS2 that does not work. It can fool a test, which is why the laboratory's method matters.
- Carrier
- Someone who has the fault. A carrier is well, is offered checks, and may never develop cancer.
- True negative
- A relative who does not carry the known family fault. Their risk from PMS2 is the same as anyone else's.
- CMMRD
- A rare childhood condition when a child inherits a faulty repair gene from both parents. It is very different from adult Lynch syndrome.
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Side by side
What does a relative's result change for them?
Carries the fault
Does not carry it
Regular colonoscopy, usually from the thirties
Routine bowel screening for their age
Women learn the womb warning signs
No extra womb checks for this gene
Their children can be offered testing as adults
Their children cannot inherit it from them
A related partner may be offered testing
Family history may still guide some checks
Being straight with you
What this page cannot tell you
It cannot tell you what your specific variant means. That is a question for the counsellor who ordered the test. It also cannot decide who in your family should hear first. That depends on relationships as much as on genes.
Where cousin marriage comes in
If you and your partner are related, you could both carry the same PMS2 fault. A child who inherits it from both parents can develop CMMRD, with cancers in childhood. If your marriage is within the family, ask whether your partner should be tested before pregnancy.
Who this does not apply to
If the PMS2 change was found only in a tumour, and not in a blood test, relatives are not tested yet. The first step is a blood test for the person who had the cancer. That kind of tumour testing is explained by your oncologist.
Commonly believed
Four things families say about testing for PMS2
"PMS2 is low risk, so my relatives do not need to know."
Lower risk still means a raised risk of bowel and womb cancer. A relative who knows can have colonoscopies that find growths early.
"Any laboratory can test my brother."
PMS2 is harder to test than most genes because of its near-copy. Choose a laboratory that knows the gene, and send your report with his sample.
"My daughter is only fifteen, so we should test her now to be safe."
Nothing changes for her until adulthood, when bowel checks come into view. Waiting lets her make the choice herself.
"It came from my mother's side, so my father's family is fine."
For this fault, yes, once testing has confirmed which side it came from. Do not assume the side without testing a parent.
Questions we are asked
Common questions about testing the family for PMS2
Does my relative need the full gene panel I had?
No. Once your fault is known, relatives are tested only for that one change. This single-site test is usually quicker and cheaper. Send your report with the sample so the laboratory can target the right spot in the real gene.
Why did my relative get an unclear result?
Sometimes the near-copy of PMS2 confuses the test. Ask whether the laboratory used a method designed for PMS2, and whether the result can be confirmed. Your counsellor can arrange this.
At what age should my children be tested?
Usually as adults, and before bowel checks would be due. Many families choose the early twenties, once the young person can decide for themselves. There is no benefit in testing a young child for adult Lynch risk.
We are a cousin marriage. Should my husband be tested?
It is worth asking. If he carries the same fault, each child could inherit it from both of you. That causes a rare, serious childhood condition. A counsellor can test him and explain the choices before pregnancy.
Can relatives abroad or in other states be tested?
Yes. They can see a counsellor where they live and send your report to their laboratory. Remote counselling is also possible. What matters is that their laboratory knows exactly which change to look for.
My relative tested negative. Are they completely clear?
They are clear of your family's PMS2 fault and can follow routine screening. If there is a lot of bowel cancer on their other side, their own doctor may still suggest earlier checks.
Do I have to tell my relatives?
No law in India requires it. Most people do, because it could help a brother or sister avoid bowel cancer. Your counsellor can help you decide who to tell first and how to put it.
Will a relative's result be shared with me?
Only if they choose to share it. Each person's result belongs to them. The counsellor will not pass it on without their consent, even within the same family.
Your Specialists
Meet CION's oncologists. Bring your family history or genetic report to them.
Our medical oncologists see people with a strong family history of cancer, arrange genetic counselling and testing where it fits, and plan the checks that follow.
Medical Oncologist
Dr. C. Raghavendra Reddy
MBBS(Gold Medal), DNB(General Medicine), DM(Medical Oncology)(Gold Medal)
Medical Oncologist
Dr. Bharati Devi Gorantla
MBBS, MD(General Medicine), DM(Medical Oncology)(Adyar,Chennai), ECMO, MRCP SCE(UK)
Medical Oncologist
Dr. Owais Mohammed
MBBS, MD (General Medicine), DrNB (Medical Oncology), ECMO, MRCP SCE (Medical Oncology) (UK)
Medical Oncologist
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Sources
- GeneReviews (NCBI) — Lynch Syndrome
- MedlinePlus Genetics — PMS2 gene
- National Cancer Institute — Genetic Testing for Inherited Cancer Susceptibility Syndromes
- NHS — Predictive genetic tests for cancer risk genes
This page is general information, not a prescription. Do not change or stop any treatment based on what you read here. If anything is worrying you, contact your own treating team — or call our helpline and we will help you reach the right specialist.
Keep reading
Related pages
Why PMS2 is hard to testThe near-copy gene, and how laboratories get round itSurveillance for PMS2 carriersThe checks a relative who tests positive is offeredCMMRD in childrenWhat happens when a child inherits two faulty copiesConsanguineous families and cascade testingTesting when partners are related
Talk to us
Need help planning who in the family to test?
Bring your PMS2 report and a rough family tree, and we will help you work out who to test first and where. One helpline serves every CION centre.