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Testing the family after an SDHx fault is found | CION Cancer Clinics
Once an SDHx fault is found in one person, their parents, brothers, sisters and children are usually offered a test for that exact change. Unlike many cancer genes, children are often tested young, because checks from childhood help. This page explains who is tested first, how it works, what each result means and why the parent it came from 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 an SDHx fault?
- Which relatives come first, and why?
- How does family testing actually work?
- What do the family testing terms mean?
- What does each result mean for a relative?
- What do families get wrong about testing relatives?
- What this page cannot tell you
- Common questions about testing the family
The short answer
Who in the family should be tested for an SDHx fault?
Once a fault is confirmed in one person, their parents, brothers, sisters and children are usually offered a test for that exact fault. Each of them has an even chance of carrying it. Relatives who test negative can usually stop worrying, and those who test positive can start planned checks early.
Why children are tested earlier than for most genes
For many inherited cancer genes, testing waits until a child is an adult. SDHx is different. Tumours can appear in teenagers, especially with SDHB, and checks from childhood genuinely help. So most guidelines suggest testing children of a carrier while they are still young, with the parents' consent and the child involved as far as their age allows.
Why the parent it came from matters
With SDHD and SDHAF2, a fault passed on by the father carries the usual risk. A fault passed on by the mother carries a much lower risk for that child. The child still needs to know, because they can pass the fault to their own children later.
Testing a relative is always a personal choice. No one should be tested without understanding what a result will mean.Who is offered a test
Which relatives come first, and why?
Testing moves outward through the family, one step at a time. Each positive result shows who should be offered a test next.
Brothers and sisters
Each full brother or sister has an even chance of carrying the fault. Adults can be tested straight away. A negative result means they did not inherit it and cannot pass it on.
Children
Each child has an even chance too. Testing is usually offered in childhood, so that a carrier child can start checks at the age the guidelines suggest for their gene.
Parents usually ask
- When should my child be tested?
- How do we explain it to them?
Parents
Testing both parents shows which side the fault came from. That tells you which uncles, aunts and cousins should be offered a test, and matters for the SDHD parent-of-origin question.
The wider family
Once the side is known, relatives on that side are offered testing in turn. In large joint families, and where relatives live in different districts, this step often takes the longest.
Not sure whether this applies to you?
Ask an oncologistStep by step
How does family testing actually work?
The fault is confirmed in the first person
Usually the relative who had a paraganglioma or phaeochromocytoma. Their report names the exact spelling change in the gene.
The counsellor draws the family tree
Who is related to whom, who has had a tumour and where everyone lives. From this the counsellor lists who should be offered a test.
Relatives are told
Often the carrier shares a family letter that explains the fault and how to arrange a test. It is simpler than explaining the genetics yourself.
Each relative is counselled and tested
A short conversation first, then a blood sample checked for the one known change. This is quicker and cheaper than the first test.
Results set the plan
Carriers start planned hormone tests and scans. Relatives who do not carry the fault return to ordinary care.
Words you will hear
What do the family testing terms mean?
- Cascade testing
- Offering a test to relatives step by step, starting with the closest, once a fault is found in one person.
- Predictive test
- A test in a well person to find out whether they carry the fault already found in the family.
- Carrier
- Someone who has the fault but no tumour. A carrier is not a patient, but does need planned checks.
- True negative
- A relative who does not carry the known family fault. Their risk returns to that of the general population.
- Parent of origin
- Which parent passed the fault on. For SDHD and SDHAF2 it changes the risk to the child.
- Family letter
- A written note a carrier can share, explaining the fault and how relatives can arrange testing.
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Side by side
What does each result mean for a relative?
Carries the family fault
Does not carry it
Starts hormone tests and scans
Needs no special checks for SDHx
Their children should be offered testing
Their children cannot inherit it from them
Tells doctors before any operation
No extra precautions are needed
May carry lower risk if from the mother
Risk is that of the general population
Commonly believed
What do families get wrong about testing relatives?
"My father is healthy, so the fault must be from my mother."
Many carriers never develop a tumour. Only a test of each parent shows where it came from. Guessing from who is well can send the family's testing down the wrong side.
"It came from my mother, so my children are safe."
With SDHD, a fault from your mother lowers your own risk. If you are a man, your children who inherit it from you carry the full risk, so they still need testing.
"Our daughters should not be tested, it will spoil marriage prospects."
A daughter who carries the fault benefits most from early checks. Counsellors can talk through what, when and how to disclose, which is a real concern for many families.
"A child is too young for this."
For SDHx, checks often begin in childhood because tumours can appear young. Testing early lets a child who does not carry the fault skip years of needless scans.
Being straight with you
What this page cannot tell you
It cannot tell you who in your family carries the fault. Only a test can, and each relative has to decide for themselves whether to have one. A counsellor can help you plan how to raise it, which relatives to approach first and what to say.
It cannot settle family tensions
Some relatives will not want to know. Some will blame the side it came from. Where parents are related by blood, as happens in some families here, the tree can be harder to read. These are common, and a counsellor who speaks Telugu can help the conversation.
Who this does not apply to
If no fault has been found in anyone yet, there is nothing specific to test relatives for. Start with the person who had the tumour. If they have died, ask whether a stored tissue block can be tested instead. What any single result means is a question for the counsellor who ordered it.
India has no dedicated law protecting people from genetic discrimination. Ask about insurance before testing, not after.Questions we are asked
Common questions about testing the family
At what age should my child be tested?
It depends on the gene. For SDHB, testing and checks usually start earlier in childhood than for the other genes. Your counsellor will suggest a timing that fits your family, so the result arrives before any checks would need to begin.
Does my relative need the full panel test I had?
No. Once your fault is known, relatives are tested for that single change only. This is quicker and costs much less than the first test. Share a copy of your report so the lab knows exactly what to look for.
My relatives live in another district. Can they still be tested?
Yes. The sample is an ordinary blood draw, and counselling can sometimes be done by video. The helpline can advise how relatives outside Hyderabad can arrange this with as little travel as possible.
What if a relative refuses to be tested?
That is their right. Give them the family letter and let them know the door stays open. Some relatives come back years later, often when they have children of their own. Pressure rarely helps.
Should my husband or wife be tested too?
Usually not, unless they have their own family history of these tumours. The children's risk comes from the parent who carries the fault. Where the couple are related by blood, mention it to the counsellor, who will decide if more testing is needed.
Can we test before or during a pregnancy?
Options exist, including testing during pregnancy and testing embryos in IVF. They raise personal and ethical questions. A counsellor can explain what is available in India, what it involves and what it costs, so you can decide calmly.
If my test is negative, can my children still inherit it?
Not from you. If you do not carry the family fault, you cannot pass it on, and your children need no testing for it. This assumes the test looked for the right change, which is why the first person's report matters.
Who explains the result to a child?
Usually the parents, with help from the counsellor. Children cope best with simple, honest explanations at their own level. Many families find it easier when the counsellor joins the first conversation.
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)
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Sources
- GeneReviews (NCBI) — Hereditary Paraganglioma-Pheochromocytoma Syndromes
- MedlinePlus Genetics — Hereditary paraganglioma-pheochromocytoma
- NHS — Predictive genetic tests for cancer risk genes
- National Cancer Institute — Genetic Testing for Inherited Cancer Susceptibility Syndromes
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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Talk to us
Need help planning who in the family to test?
Tell us who carries the fault and which relatives you are thinking about. We will help you arrange counselling and testing, including for relatives in the districts. One helpline serves every CION centre.