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The Fanconi anaemia genes: what they do and why they matter | CION Cancer Clinics
The Fanconi anaemia genes are a team of more than twenty genes whose job is to repair one especially dangerous kind of DNA damage. When both copies of one of these genes are faulty, a person has Fanconi anaemia, a rare inherited condition that wears out the bone marrow and raises cancer risk from a young age. One faulty copy usually causes no illness. This page explains the difference. 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
- What do the Fanconi anaemia genes actually do?
- One faulty copy or two: which situation are you in?
- How does a repair fault lead to marrow failure and cancer?
- The words you will meet, in plain language
- A carrier and a person with Fanconi anaemia compared
- What this page cannot tell you
- Four things families tell us, and what is actually true
- Common questions about the Fanconi anaemia genes
The short answer
What do the Fanconi anaemia genes actually do?
They repair one especially dangerous kind of DNA damage, where the two strands of DNA get stuck together. More than twenty genes share this job, working as one repair team. If the team is missing a member, that damage builds up, and the cells that divide most, such as blood stem cells, are hurt first.
Why the condition carries the genes' name
Fanconi anaemia is a rare inherited condition in which the bone marrow slowly stops making enough blood cells. The genes were named after it because that is how doctors first found them. Each gene has a short code beginning with FANC, such as FANCA or FANCC. FANCA is the one found most often, in India as elsewhere.
Why it matters beyond the blood
The same repair team protects every tissue. When it fails, the risk of leukaemia and of certain cancers of the mouth and throat rises, often at a young age. Some of these genes are also well-known adult cancer genes. BRCA2 and PALB2 are both members of the team.
Most people with a fault in one of these genes are carriers who stay healthy. Fanconi anaemia needs a fault in both copies.Four different situations
One faulty copy or two: which situation are you in?
The same gene name on a report can mean very different things. The number of faulty copies is what decides it.
Two faulty copies
This is Fanconi anaemia. It is usually found in childhood, often because blood counts fall or a child is born with thumb, arm or kidney differences. It needs care from a haematologist, a blood specialist, for life.
One faulty copy, in most FANC genes
You are a carrier. The working copy does the job, and you do not have Fanconi anaemia. The main reason it matters is for your children, if your partner carries a fault in the same gene.
One faulty copy, in a gene that is also an adult cancer gene
BRCA2, PALB2, BRIP1, RAD51C and BRCA1 all belong to the repair team. One faulty copy of these raises your own adult cancer risk. You follow the programme for that gene.
Usually means
- Earlier or extra screening for you
- Testing offered to your relatives
No fault found
If a relative has a known fault and you tested negative for it, you are not a carrier. If nobody's fault is known, a negative result is less certain.
Not sure whether this applies to you?
Ask an oncologistHow the damage builds
How does a repair fault lead to marrow failure and cancer?
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Everyday chemistry glues DNA strands together
Normal body processes make by-products that can stick the two strands of DNA together. Alcohol produces more of them. A cell cannot copy its DNA until the strands are freed.
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The repair team finds the damage and cuts it free
Several FANC proteins first gather into a group that flags the damage. Others then cut the strands apart and rebuild the missing piece, using the matching copy as a guide.
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A missing member stalls the whole team
When both copies of one FANC gene are faulty, that step never happens. The damage stays, or is patched badly. Chromosomes break and rejoin in the wrong places.
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Blood stem cells wear out first
Bone marrow stem cells divide constantly, so they pile up damage fastest. Over years they die off, and counts of red cells, white cells and platelets fall.
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Damaged cells that survive can become cancer
A cell that lives on with scrambled chromosomes can grow unchecked. That is why leukaemia, and cancers of the mouth and throat, appear earlier in Fanconi anaemia than in anyone else.
On your report
The words you will meet, in plain language
- FANC gene
- Any of the genes in the Fanconi repair team. The letter after FANC simply tells them apart.
- Crosslink
- A spot where the two strands of DNA are stuck together. This is the damage the team exists to fix.
- Biallelic
- Both copies of the gene are faulty. In most FANC genes this is what causes Fanconi anaemia.
- Carrier
- Someone with one faulty copy and one working copy. For most FANC genes a carrier is healthy.
- Chromosome breakage test
- A blood test that stresses cells with a chemical and counts the breaks. Cells from someone with Fanconi anaemia break far more.
- Mosaicism
- Some blood cells have repaired their own fault by chance. It can make a blood test look normal, so a skin sample is sometimes needed.
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Side by side
A carrier and a person with Fanconi anaemia compared
Carrier, one faulty copy
Fanconi anaemia, two faulty copies
Blood counts are normal
The bone marrow usually fails over time
Standard cancer treatment is usually safe
Many chemotherapy drugs and radiation need big dose cuts
No routine checks, unless the gene is BRCA2, PALB2 or similar
Regular marrow, mouth and gynaecological checks for life
Matters mainly for children with a carrier partner
Brothers and sisters need testing too
Being straight with you
What this page cannot tell you
It cannot tell you what your own result means. Laboratories name the gene and the exact change, and whether that change breaks the gene is a judgement. What your specific variant means is a question for the counsellor who ordered the test.
It cannot give you a personal risk figure
Cancer risk in Fanconi anaemia differs between genes and between people. Whether a transplant was done, and how it went, changes it too. For most carriers, studies so far are small and have not shown a clear rise in risk. A haematologist who knows the family is the right person to weigh this.
Who this does not apply to
Most people never need a FANC gene test. It is considered when a child has falling blood counts or typical birth differences, when a young adult develops a mouth cancer without tobacco use, or when a relative has a known fault. If none of these fits your family, this page is background reading.
Families in which cousins marry are more likely to have two carriers as parents. That is a reason to ask, not a reason to worry.Commonly believed
Four things families tell us, and what is actually true
"Anaemia is in the name, so it is just a low haemoglobin."
The name is misleading. Fanconi anaemia affects all three kinds of blood cell, not just red cells. It also affects DNA repair throughout the body. Iron tablets do not help it.
"My child looks normal, so it cannot be Fanconi anaemia."
Many children with the condition have no visible birth differences at all. Some are only found when blood counts fall, or when a brother or sister is tested.
"We are both healthy, so we cannot carry anything."
Carriers of most FANC genes are completely well and usually have no idea. It is often an affected child that reveals both parents are carriers.
"A carrier result means I will get cancer."
For most FANC genes, a single faulty copy has not been shown to raise your own risk clearly. The exceptions are the genes that are also adult cancer genes, such as BRCA2, and those carry their own advice.
Questions we are asked
Common questions about the Fanconi anaemia genes
How many Fanconi anaemia genes are there?
More than twenty have been found, and the list still grows as research continues. A fault in any one of them can cause the condition when both copies are affected. FANCA accounts for the largest share of families, which is why many laboratories look at it first or read the whole group together on one panel.
Is Fanconi anaemia always inherited from both parents?
Almost always. Each parent usually passes on one faulty copy. One gene, FANCB, sits on the X chromosome and is passed from mother to son. A very small number of cases arise from a brand-new fault that neither parent carries.
Why is my BRCA2 report linked to Fanconi anaemia?
BRCA2 is one of the repair team. One faulty copy raises adult breast, ovarian, prostate and pancreatic cancer risk. Two faulty copies cause a severe form of Fanconi anaemia in a child. A report may mention both, and a counsellor will explain which applies to you.
Can Fanconi anaemia be treated?
A bone marrow transplant can replace the failing marrow, but it does not fix the gene in the rest of the body. The cancer risk in the mouth and throat remains, and may rise, so checks continue for life. Gene therapy is being studied, and those studies so far are small.
Why is alcohol discussed so often?
The body breaks alcohol down into a chemical that damages DNA in exactly the way this repair team fixes. For someone with Fanconi anaemia, alcohol adds to that damage. Tobacco, including chewed tobacco and gutka, raises mouth cancer risk further.
Does a carrier need regular check-ups?
For most FANC genes, no extra checks are advised for the carrier. The exception is a carrier of BRCA2, PALB2, BRIP1, RAD51C or BRCA1, who follows the screening plan for that gene. Your counsellor will tell you which group you fall into.
Can the gene fault be corrected?
No. A gene fault present from birth cannot be corrected or reversed in every cell. Care focuses on the marrow, on catching cancer early, and on avoiding things that add DNA damage. A transplant replaces the blood-forming cells only.
Where do I start if a child's blood counts keep falling?
Ask the treating doctor whether Fanconi anaemia has been considered, especially before any chemotherapy or transplant is planned. A chromosome breakage test answers the question. Call the CION helpline if you are unsure where to begin, and we will point you to a haematologist.
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 — FANCA gene
- 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
Fanconi anaemia genes: which cancers and what riskWhich cancers the condition raises, and at what agesA Fanconi anaemia gene result: what happens nextThe first steps after a positive resultTesting the family for the Fanconi anaemia genesWho else should be tested, and in what orderWhy chemotherapy and radiation doses must be reducedWhy standard treatment can be dangerous in this condition
Talk to us
Has a FANC gene appeared on a report in your family?
Tell us what the report says and who it belongs to. We will help you reach a haematologist or genetic counsellor who can explain it properly. One helpline serves every CION centre.