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Testing your family for an MSH2 fault | CION Cancer Clinics
Once an MSH2 fault is found, each parent, brother, sister and child of the carrier has a one in two chance of sharing it. They can be tested for that one exact change, which is simpler and cheaper than the first test. A negative result is genuinely reassuring. This page explains who to test first, how the test works, and what each result means. 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 MSH2?
- Which relatives come first, and why?
- How does a relative actually get tested?
- What do the terms in family testing mean?
- What changes for a relative after the result?
- What this page cannot tell you
- Four things families say about testing, and what is true
- Common questions about testing relatives for MSH2
The short answer
Who in the family should be tested for MSH2?
Start with the closest relatives of the person who carries the fault: parents, brothers, sisters and adult children. Each of them has a one in two chance of carrying the same MSH2 fault. They are tested for that one exact change, which is simpler and cheaper than a full gene panel. Testing then moves outwards, one branch of the family at a time.
Why the carrier's report matters so much
A relative's laboratory needs to know exactly which change to look for. Without a copy of the original report, a relative may be sent for a broad panel that costs more and can raise confusing extra findings. With it, the test is targeted and the answer is clear.
Why a negative result here is real reassurance
When the family fault is known, a relative who does not carry it has a true negative. Their bowel and womb risk goes back to that of the general population, at least from this side of the family. They can stop the frequent checks, and their children cannot inherit the fault from them.
When the parents are no longer alive
Families often worry that testing stops when the older generation has died. It does not. Brothers, sisters and cousins can still be tested for the known fault, and the pattern of who carries it usually shows which side it came from. Sometimes stored tissue from a parent's old surgery can also be tested, although this is not always needed.
Testing is always a choice. Some relatives decide not to know, and that is their right.In order
Which relatives come first, and why?
The order follows who is most likely to carry the fault and who would benefit soonest.
Brothers and sisters
Each has a one in two chance. Older siblings may already be past the age when colonoscopy should have started, so they are often the most urgent.
Parents
Testing a living parent shows which side the fault came from. That tells you which aunts, uncles and cousins to approach next.
Adult children
Usually offered from the late teens or early twenties, in time for the first colonoscopy. Younger children normally wait, because checks do not begin in childhood.
The wider family
Once the side is known, the relatives on that side are offered testing.
Often includes
- Aunts and uncles
- First cousins
- Both sides, where parents are related by marriage
Not sure whether this applies to you?
Ask an oncologistStep by step
How does a relative actually get tested?
The carrier shares the result
Many counsellors give the carrier a family letter explaining the fault and what testing involves. Relatives can take it to any genetics clinic.
The relative sees a counsellor first
A short session covers what a positive or negative result would mean for them, their work and their children, before any blood is taken.
A targeted blood test
The laboratory checks only for the family's exact MSH2 change. If the family fault is a large deletion, the lab uses a method that can find deletions.
The result is given in person
A positive result leads to a surveillance plan. A negative result means routine screening for their age, with nothing extra to do.
Words you will hear
What do the terms in family testing mean?
- Cascade testing
- Testing relatives step by step, starting with the closest and moving outwards as each new carrier is found.
- First-degree relative
- A parent, brother, sister or child. They share half their genes with you.
- Targeted test
- A test for one known family change only. It is also called a single-site or known-variant test.
- Predictive test
- A test in a healthy person to find out whether they carry a fault already found in the family.
- True negative
- A clear result for a known family fault. It means that fault was not passed to you.
- Family letter
- A letter from the counsellor that a carrier can share, naming the fault so relatives can be tested.
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Side by side
What changes for a relative after the result?
Carries the family fault
Does not carry it
Colonoscopy every one to two years
Routine screening for their age
Women plan for the womb and ovaries
No extra gynaecology checks needed
Their own children can be offered testing
Their children cannot inherit it from them
Aspirin may be discussed
Nothing further to discuss for this fault
Being straight with you
What this page cannot tell you
It cannot decide how to tell your family. In many Indian households, the news reaches a joint family, in-laws and questions about marriage all at once. How and when you share it is a personal decision, and a counsellor can help you plan the conversation, sometimes in Telugu.
It cannot promise protection from insurers
India has no dedicated law on genetic discrimination in insurance. Relatives who are weighing a test may want to discuss cover with a counsellor before testing, not afterwards.
Who this does not apply to
Relatives by marriage, such as a spouse or in-laws, share none of your genes and do not need this test for your fault. Relatives on the side of the family that did not pass on the fault do not need MSH2 testing. Nor do relatives of someone whose report shows only a variant of uncertain significance, because there is nothing confirmed to test for. What a specific report means is a question for the counsellor who ordered the test.
Commonly believed
Four things families say about testing, and what is true
"My brother tested negative, so I must be negative too."
Each brother and sister has their own separate chance. One sibling's result tells you nothing about yours. Only your own test can answer it.
"Only the women in the family need to be tested."
Men carry and pass on MSH2 in exactly the same way. They also face bowel and urinary tract risks of their own, so they benefit from knowing.
"We should test the children now, while they are small."
Checks for MSH2 do not start in childhood, so testing normally waits until the young person can make the choice for themselves.
"Every relative needs the full expensive gene panel."
Once the family fault is known, a targeted test for that one change is usually enough. It is simpler, faster and costs less.
Questions we are asked
Common questions about testing relatives for MSH2
How do I tell my relatives about an MSH2 result?
Many people start with a family letter from their counsellor and a copy of the report. You can share it in person, by post or on WhatsApp. Keep it factual: which gene, that testing is available, and that a negative result is genuinely reassuring. Your counsellor can help you plan harder conversations.
Can a relative in another city or abroad be tested?
Yes. Any accredited genetics service can run a targeted test if it has a copy of the original report. Relatives abroad can usually be tested through their own health system. Some families in districts use telephone counselling to avoid extra travel.
What if a relative refuses to be tested?
That is their right. You can still tell them about the symptoms that matter and suggest they discuss earlier colonoscopy with a doctor. Many people come back to the question later, often around a marriage, a pregnancy or a new diagnosis in the family.
At what age can my children be tested?
Usually from the late teens or early twenties, before the first colonoscopy would be due. Until then a result would not change anything for them. Waiting also lets them decide for themselves whether they want to know.
My parents were related before marriage. Does that change anything?
It can mean both sides of the family need to be considered, not only one. Rarely, a child inherits a mismatch repair fault from both parents, which is a different and more serious condition in childhood. Tell your counsellor about the relationship at the start.
Is a targeted test cheaper than the first test?
Usually, yes. It looks at one known change rather than many genes, so it tends to cost less and report sooner. Prices vary between laboratories. Ask for a written quote and ask whether the family's original report is needed.
Does a negative relative still need any screening?
They follow the same screening as anyone else their age. If the other side of their family has its own history of cancer, that can still count. Their counsellor will look at the whole picture before closing the question.
Who can help me organise testing for the family?
The genetic counsellor who gave your result is the best starting point. They can write the family letter and suggest where relatives can be tested. Call the CION helpline if you are unsure who to approach first.
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
- National Cancer Institute — Genetic Testing for Inherited Cancer Susceptibility Syndromes
- MedlinePlus Genetics — Lynch syndrome
- 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.
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Want help organising testing for your relatives?
Bring your MSH2 report and a list of relatives, and we will help you plan who to approach and where they can be tested. One helpline serves every CION centre.