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Testing the family for the Fanconi anaemia genes | CION Cancer Clinics
When a child has Fanconi anaemia, every brother and sister should be tested, even those who seem healthy. Parents are usually tested next, to confirm they are carriers. Aunts, uncles and cousins can choose carrier testing later, often before marriage or a pregnancy. This page explains who to test, in what order, and what each result means for that person. 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. Basudev PokhrelConsultant Haematologist · last reviewed September 2026, next review due September 2027
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On this page
- Who in the family should be tested for Fanconi anaemia?
- What does the result mean for each person in the family?
- How is family testing done, step by step?
- The terms used in family testing, in plain language
- Testing a sibling compared with testing a wider relative
- What this page cannot tell you
- Four things families tell us, and what is actually true
- Common questions about testing the family
The short answer
Who in the family should be tested for Fanconi anaemia?
Every brother and sister of a child with Fanconi anaemia should be tested, even if they look perfectly well. Fanconi anaemia is a rare inherited condition in which the bone marrow slowly stops making enough blood cells. Parents are usually tested next, to confirm they are carriers. Wider relatives can choose carrier testing later, usually around the time they plan a family.
Why brothers and sisters come first
A sibling can have the condition without any visible signs. Finding it early means checks can start before the marrow fails. It also matters for transplant, because a brother or sister is often the best donor, and a donor must not have the condition themselves.
Why parents are tested
In almost every family, each parent carries one faulty copy and is healthy. Testing them confirms the pattern and shows which fault came from which side. That tells the counsellor which relatives on each side might also be carriers. If the child's gene is BRCA2 or PALB2, this step has a second purpose. Each parent then needs advice about their own adult cancer risk, and so do their brothers and sisters.
Carrier testing for a child is usually left until they are old enough to decide. Testing a child for the condition itself is different, and is done early.Relative by relative
What does the result mean for each person in the family?
Most FANC genes pass down in the same way. Both parents must pass on a faulty copy for a child to be affected.
Brothers and sisters
When both parents are carriers, each child has a one in four chance of having Fanconi anaemia. Each has a two in four chance of being a healthy carrier, and a one in four chance of neither. A brother or sister who is a carrier stays well.
Parents
Almost always carriers, and healthy. The exception is when the gene is BRCA2, PALB2, BRIP1, RAD51C or BRCA1. Then each parent carries an adult cancer gene and needs advice for their own health.
Aunts, uncles and cousins
Some will be carriers. This rarely affects their own health, but it matters if they marry within the family, where two carriers are more likely to meet.
Worth testing when
- They plan to marry a relative
- They are planning a pregnancy
- Their partner's family has the condition
Children of someone with Fanconi anaemia
Every child inherits one faulty copy and is at least a carrier. A child is affected only if the other parent is also a carrier. Fertility is often reduced in Fanconi anaemia, so many adults with the condition seek advice before trying for a family.
Not sure whether this applies to you?
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How is family testing done, step by step?
Pin down the exact faults
The child's two faults are identified first. Once they are known, relatives can have a targeted test that looks only for those two changes. It is simpler, and usually cheaper, than a full panel.
Test each brother and sister
A targeted gene test, often with a chromosome breakage test, shows whether a sibling has the condition, is a carrier, or has neither.
Confirm the parents
Each parent is tested for the fault expected on their side. This rules out a rare new fault and guides testing among uncles, aunts and cousins.
Offer wider relatives a choice
The family is given a letter explaining the fault. Adult relatives can take it to a counsellor when they are ready. Nobody is obliged to be tested.
Words you will hear
The terms used in family testing, in plain language
- Cascade testing
- Offering a test to relatives, one step at a time, once a fault is found in one person.
- Targeted test
- A test for the exact faults already found in the family, rather than a search of every gene.
- Carrier
- Someone with one faulty copy and one working copy. For most FANC genes a carrier is healthy.
- Consanguinity
- Marriage between blood relatives, such as cousins or uncle and niece. It raises the chance both partners carry the same fault.
- Prenatal diagnosis
- Testing a pregnancy for the family's known faults, using a small sample from the placenta or the fluid around the baby.
- Preimplantation testing
- Testing embryos made through IVF, before one is placed in the womb.
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Side by side
Testing a sibling compared with testing a wider relative
Brother or sister
Aunt, uncle or cousin
Tested in childhood, soon after the diagnosis
Tested as an adult, when they choose
Asks whether they have the condition
Asks whether they are a carrier
A positive result starts regular checks
A positive result mainly shapes family planning
Also decides whether they can donate marrow
Donation is rarely part of the question
Being straight with you
What this page cannot tell you
It cannot tell you which of your relatives carries the fault. Only a test can do that. It also cannot tell you how a family should handle the news. Some families share results openly. Others need time, and a counsellor can help plan how to tell each person.
It cannot interpret a relative's report
A carrier result in one gene can mean something different from the same word in another. What your specific variant means is a question for the counsellor who ordered the test. If a relative was tested elsewhere, bring a copy of their report. It cannot tell you what testing will cost either. A targeted test for a known family fault usually costs less than the first test, and asking for a written estimate before sampling avoids surprises.
Who this does not apply to
If nobody in your family has Fanconi anaemia or a known FANC fault, family testing does not arise. Most people do not need this test. The exception is a couple who are related to each other and want to know their chances before a pregnancy.
Choices in pregnancy, including IVF with embryo testing, are personal and complex. A counsellor explains them without steering you.Commonly believed
Four things families tell us, and what is actually true
"Our other children are healthy, so there is no need to test them."
Fanconi anaemia can stay hidden until the blood counts start to fall. A sibling who seems well can still have it, and finding it early changes their care.
"It came from the mother's side."
For most FANC genes, both parents pass on one faulty copy. Neither side is to blame, and neither parent could have known.
"If one child is affected, the next one will be fine."
Chance has no memory. Each pregnancy carries the same one in four chance, whatever happened before.
"Carriers should not marry."
Carriers can marry and have healthy children. A child is affected only if both partners carry a fault in the same gene. Testing the partner is what answers that question.
Questions we are asked
Common questions about testing the family
What sample is needed from relatives?
A blood sample is usual. Saliva can work for a targeted gene test, but the chromosome breakage test needs blood. A relative living in a district can often give a sample locally, and the laboratory will say how it should be sent.
Should our youngest child be tested even as a baby?
Yes, testing for the condition itself is advised in brothers and sisters of any age. Early knowledge allows checks to begin in time. Carrier testing is different, and is usually left until the child is an adult.
Can a sibling who is a carrier donate marrow?
Often yes. A carrier has healthy marrow and can usually donate if the tissue type matches. The transplant team makes the final decision after its own checks.
What if the gene is FANCB?
FANCB sits on the X chromosome, so it is passed from a carrier mother, and mainly affects boys. The mother's sisters may also be carriers. Your counsellor will draw the family tree differently for this gene.
We are cousins. Should we be tested before a pregnancy?
If Fanconi anaemia or any recessive condition is known in the family, yes, it is worth asking. If not, a counsellor can tell you whether wider carrier screening makes sense for you. Many related couples have healthy children.
Can a pregnancy be tested?
Yes, once the family's exact faults are known. A sample is taken from the placenta or the fluid around the baby. Some couples choose IVF with embryo testing instead. Both are personal choices, and neither is required.
Do I have to tell my relatives?
No law requires it, and the choice is yours. Many families find a written family letter from the counsellor easier than explaining it themselves. It can be shared on WhatsApp and read in private.
Where can the family start?
With the affected child's report and a genetic counsellor. Call the CION helpline if you are unsure who to approach. We will help arrange counselling, including in Telugu, and advise on testing relatives who live outside Hyderabad.
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) — Fanconi Anemia
- MedlinePlus Genetics — Fanconi anemia
- MedlinePlus Genetics — What are the different ways a genetic condition can be inherited?
- 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.
Keep reading
Related pages
A Fanconi anaemia gene result: what happens nextThe first steps after a positive resultThe Fanconi anaemia genes: what they doWhy one faulty copy and two faulty copies differConsanguinity and cancer riskWhat marrying within the family does and does not changeCascade testing: how a result moves through a familyThe general method behind family testing
Talk to us
Need help planning tests for the family?
Tell us who has been diagnosed and which relatives want answers. We will help arrange counselling and testing, including for relatives outside Hyderabad. One helpline serves every CION centre.