Medical Oncologist
CION Cancer Clinics
Testing your family for an FLCN fault | CION Cancer Clinics
Once one person carries an FLCN fault, their parents, brothers, sisters and adult children can be tested for that exact fault. Each has a one in two chance of carrying it. Carriers start kidney scans and find problems early. Non-carriers can skip them altogether. This page explains who is tested first, how the test works, and what each result means for the rest of the family. 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 FLCN?
- What does a test mean for each family member?
- How does family testing actually happen?
- What do the family-testing words mean?
- What does each result mean for a relative?
- What can this page not tell you?
- What do families get wrong about FLCN testing?
- Common questions about testing the family for FLCN
The short answer
Who in the family should be tested for FLCN?
Once one person is found to carry an FLCN fault, their parents, brothers, sisters and adult children should be offered a test for that exact fault. Each of them has a one in two chance of carrying it. The test is simpler and usually cheaper than the first one, because the laboratory knows exactly what to look for.
Why it is worth doing
An FLCN fault causes Birt-Hogg-Dubé syndrome, or BHD, which raises the risk of kidney tumours. Relatives who carry it can start regular kidney scans and find any tumour while it is small. Relatives who do not carry it can stop worrying and skip those scans altogether. Both answers are useful.
How the testing spreads
Testing usually starts with the closest relatives. When one of them tests positive, their own children and siblings are offered a test next. Doctors call this cascade testing. It moves through the family one branch at a time, and it follows the side the fault came from.
Every relative decides for themselves. Nobody should be tested because they were pressured.Relative by relative
What does a test mean for each family member?
The same result means different things depending on who you are in the family tree.
Brothers and sisters
Each has a one in two chance of carrying the fault. They are usually the first relatives offered a test, alongside parents.
Parents
Testing a parent shows which side of the family the fault came from. That tells you which aunts, uncles and cousins also need to be told.
If a parent has died, the family history on each side can still point the way.Adult children
Each has a one in two chance. Because kidney scans begin in adult life, testing is usually offered once they are adults and can choose for themselves.
Worth talking through first
- Timing around marriage
- Insurance, before the test
- Who they want to tell
Wider family
Aunts, uncles and cousins on the side the fault came from are offered testing next. Relatives who live in another state or abroad can usually be tested near home.
Not sure whether this applies to you?
Ask an oncologistStep by step
How does family testing actually happen?
The first carrier shares the report
The relative needs a copy of the original report showing the exact variant. Without it, the laboratory cannot do a targeted test.
A counselling session
A genetic counsellor explains what a positive or negative result would mean, and checks the relative wants to go ahead. This can be done in Telugu, in person or by video.
A blood or saliva sample
The laboratory checks only for the family's known fault. This is faster and usually costs less than the first person's test.
Results and next steps
A carrier is referred for a kidney scan plan. A non-carrier is told they do not need BHD scans, and nor do their children from this line.
Words you will hear
What do the family-testing words mean?
- Cascade testing
- Testing relatives one branch at a time, starting closest to the person who carries the fault.
- Targeted or familial variant test
- A test that looks only for the exact fault already found in the family, rather than reading the whole gene again.
- First-degree relative
- A parent, brother, sister or child. These are the relatives with a one in two chance.
- Dominant inheritance
- One faulty copy from either parent is enough to raise risk. BHD is passed on this way.
- True negative
- A relative tested for the known family fault who does not carry it. Their BHD risk is the same as anyone else's.
- Pedigree
- The family tree your counsellor draws, marking who had kidney tumours, lung collapses or skin bumps.
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Side by side
What does each result mean for a relative?
The relative carries the fault
The relative does not carry it
Regular kidney MRI from early adulthood
No BHD kidney scans needed
Their own children can be offered a test
Their children cannot inherit it from them
Knows the signs of a collapsed lung
Ordinary health checks for their age
Their siblings may also need testing
That branch of the family can stop there
Being straight with you
What can this page not tell you?
It cannot tell you which relatives in your family should be tested first. That depends on who is alive, who has had symptoms and which side the fault came from. What your specific variant means is a question for the counsellor who ordered the test.
It cannot make the conversation easy
Telling relatives is often the hardest part. Some families worry about marriage prospects, and some relatives would rather not know. A counsellor can help you plan what to say, and many clinics provide a family letter you can share on WhatsApp or in person.
Who this does not apply to
Relatives on the side of the family the fault did not come from are not at raised risk and do not need testing. Partners and in-laws do not need testing either, because BHD needs only one faulty copy. If no fault has been found in anyone yet, testing well relatives is usually not the right first step.
India has no specific law on genetic discrimination in insurance. Raise this with your counsellor before testing, not after.Commonly believed
What do families get wrong about FLCN testing?
"My brother tested positive, so I must carry it too."
Not necessarily. Each sibling has a separate one in two chance, like a coin toss for each child. One sibling's result does not decide another's.
"I have no symptoms, so I do not need a test."
Many carriers have no skin bumps and no lung trouble. Kidney tumours give no warning while small. A test is the only way to know.
"Only the women in the family need testing."
BHD passes equally to sons and daughters, and men and women carry the same kidney risk. Leaving men out is a common way the fault is missed.
"If I test negative, my children should still be tested."
If you were tested for the known family fault and do not carry it, you cannot pass it on. Your children do not need testing for it.
Questions we are asked
Common questions about testing the family for FLCN
Should my children be tested now?
Usually not while they are young. BHD kidney tumours are very uncommon in childhood, and scans start in adult life. Most families wait until the child is an adult and can decide. Your counsellor will talk through your situation.
How much does a family test cost?
A targeted test for a known family fault usually costs much less than the first person's panel test. Prices vary between laboratories. Ask the CION helpline for current rates, and check insurance or scheme cover before the sample is taken.
Can relatives abroad or in another state be tested?
Yes. They need a copy of the original report and a local genetics service or laboratory. Counselling can often happen by video. The result is just as reliable wherever the sample is taken.
What if a relative refuses to be tested?
That is their right. You can share the information and the family letter, and leave the door open. Some relatives change their mind later, often after a life event or a conversation with their own doctor.
Do both parents need to be tested?
Testing both, where possible, shows which side the fault came from. That tells you which aunts, uncles and cousins should be told. If neither parent carries it, the fault may have started with you.
Does a cousin marriage change the risk?
BHD needs only one faulty copy, so a cousin marriage does not change a child's chance in the usual way. It does mean the fault may sit on both sides of the tree, so draw both sides fully for your counsellor.
Can a relative who already had a kidney tumour be tested?
Yes, and their result is especially useful. If a relative has died, stored tissue from an old operation can sometimes be tested. Ask the hospital that treated them whether a tissue block was kept.
Where do relatives start?
With a copy of your report and a genetic counselling appointment. Call the CION helpline and we will help your relatives book a session, in Telugu if they prefer.
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) — Birt-Hogg-Dubé Syndrome
- MedlinePlus Genetics — Birt-Hogg-Dubé syndrome
- 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.
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Need help telling or testing your relatives?
Tell us who in the family carries the fault and who you want to reach. We will help arrange counselling and targeted testing for them. One helpline serves every CION centre.