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The FH gene: what it does and why it matters | CION Cancer Clinics
The FH gene makes an enzyme that helps your cells turn food into energy. When one copy carries an inherited fault, the chance of skin bumps, early fibroids and an aggressive kidney cancer goes up. The condition is called HLRCC. This page explains what the gene does, how a faulty copy leads to tumours, and why carriers are offered yearly kidney scans. 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
- What does the FH gene actually do?
- Which parts of the body does an FH fault affect?
- How does a faulty FH gene lead to a tumour?
- What do the words on an FH report mean?
- What is the difference between one faulty copy and two?
- What this page cannot tell you
- Four things families believe about FH, and what is true
- Common questions about the FH gene
The short answer
What does the FH gene actually do?
The FH gene carries the instructions for an enzyme called fumarate hydratase. It works inside the mitochondria, the tiny power stations in every cell, as one step in the chain that turns food into energy. Its job is to change a chemical called fumarate into another called malate.
Why an energy gene can cause tumours
When the enzyme is missing, fumarate piles up inside the cell. At high levels it fools the cell into acting as if it were short of oxygen. The cell switches on growth signals and starts building new blood vessels. That is why FH is called a tumour suppressor gene, meaning a gene whose normal work keeps growth in check.
What an inherited fault means
Someone with an inherited FH fault is born with one working copy instead of two. Their cells work normally for years. Trouble starts only if a single cell in the skin, the womb or the kidney loses the remaining copy. The condition this causes is called hereditary leiomyomatosis and renal cell cancer, or HLRCC.
Newer reports may call it FH tumour predisposition syndrome. It is the same condition under a newer name.Where it shows up
Which parts of the body does an FH fault affect?
Three places are affected in most families. A fourth group of links is real but far less certain.
Skin
Firm bumps, skin-coloured or reddish, usually on the arms, chest or back. They are called cutaneous leiomyomas, meaning small growths of smooth muscle in the skin. They are not cancer.
Often
- Painful in cold weather
- Tender when touched
- Slowly growing in number
Womb
Most women who carry an FH fault develop fibroids. They tend to appear earlier than usual, often in the twenties or thirties, and there are usually several. Heavy periods and pelvic pain are common.
Fibroids are very common in all women. On their own they are rarely a sign of FH.Kidneys
A minority of carriers develop kidney cancer, but this is the risk that matters most. The tumour is called FH-deficient renal cell carcinoma. It can spread while it is still small, which is why yearly scans are offered.
Less certain links
Some studies link FH faults to rare tumours of the adrenal gland and nearby nerve tissue, called phaeochromocytoma and paraganglioma. A rare cancer of the womb muscle has also been reported. Evidence for both is limited.
Not sure whether this applies to you?
Ask an oncologistFrom gene to tumour
How does a faulty FH gene lead to a tumour?
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You carry two copies of the FH gene
One came from each parent. One working copy is enough to make the enzyme and keep fumarate at a safe level.
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An inherited fault removes one copy from birth
Every cell in the body starts with a single working copy. The enzyme is still made, and nothing looks different.
-
The second copy can be lost in one cell
Copying errors when cells divide can knock out the remaining copy in a single cell of the skin, womb or kidney. That cell now makes no working enzyme.
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Fumarate builds up inside that cell
The cell reads the build-up as a shortage of oxygen. It turns on growth signals and draws in new blood vessels.
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A growth may form, but not always
In the skin and womb the result is usually a harmless lump. In the kidney it can be cancer. Whether the second copy is ever lost is partly chance, so relatives with the same fault can have very different lives.
On your report
What do the words on an FH report mean?
- FH
- Short for fumarate hydratase, the enzyme this gene makes. Some reports call the enzyme fumarase. Both names mean the same thing.
- HLRCC
- Hereditary leiomyomatosis and renal cell cancer. The name lists the two main features: smooth muscle growths and kidney cancer.
- Leiomyoma
- A harmless growth of smooth muscle. In the skin it is a small bump. In the womb it is a fibroid.
- Pathogenic variant
- A spelling change in the gene that is known to stop it working. Likely pathogenic is treated the same way in practice.
- Germline
- Present in every cell from birth and able to be passed on. A fault found only inside a tumour is called somatic.
- FH-deficient
- A pathology term meaning the tumour cells have lost the enzyme. It is a strong clue, but a blood test is still needed to confirm an inherited fault.
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Side by side
What is the difference between one faulty copy and two?
One faulty copy
Two faulty copies
Inherited from one parent
Inherited from both parents, one copy from each
Causes HLRCC, with effects in adult life
Causes fumarase deficiency, a severe illness from infancy
Skin bumps, fibroids and a kidney cancer risk
Affects brain development, feeding and growth
Each child has a one in two chance of inheriting it
Each pregnancy of two carrier parents has a one in four chance
Managed with regular checks
Needs specialist children's metabolic care
Being straight with you
What this page cannot tell you
It cannot tell you whether your family carries an FH fault. That needs a genetic counsellor who has drawn your family tree and, where possible, arranged a blood test for the relative who had kidney cancer or early fibroids. Reading about the gene cannot stand in for that conversation.
It cannot read your report for you
An FH report can list a variant that is clearly harmful, one that is probably harmful, or one of uncertain meaning. These lead to very different plans. What your specific variant means is a question for the counsellor who ordered the test. A tumour found to be FH-deficient is a separate question, handled with our targeted therapy team. Only a blood test answers whether the fault is inherited.
Who this does not apply to
Most people with fibroids do not carry an FH fault, and neither do most people with kidney cancer. A single fibroid found in your forties, with no skin bumps and no kidney cancer in the family, is not a reason to test. A counsellor will tell you that plainly.
Commonly believed
Four things families believe about FH, and what is true
"FH is the high cholesterol condition."
Not on this page. Familial hypercholesterolaemia is also shortened to FH, and it is a different inherited condition that affects the heart. If a report or a relative says FH, check which one is meant before you worry.
"The skin bumps are only cosmetic, so they do not matter."
The bumps themselves are harmless. They matter because they are often the first visible sign of the gene fault, years before any kidney problem. A dermatologist who spots them can start the whole family on the right path.
"Removing the womb removes the risk."
A hysterectomy ends the fibroid problem. It does nothing for the kidneys, which still need their yearly scan. Men carry the same kidney risk too.
"Nobody in our family had kidney cancer, so we are safe."
Most carriers never develop kidney cancer, so many families have no kidney history at all. Early fibroids and skin bumps across generations can be the only clue.
Questions we are asked
Common questions about the FH gene
Is an FH fault the same as having cancer?
No. It means your cells start life with one working copy of the gene instead of two. Most carriers develop skin bumps or fibroids, which are not cancer. A smaller group develop kidney cancer, which is why regular scans matter more than the label itself.
Can men carry an FH fault?
Yes. Men inherit and pass on the fault exactly as women do. They can develop the skin bumps and they carry the same kidney risk. Only the fibroids are limited to women, so a man's own history may look quieter than his sister's.
Does every child of a carrier inherit it?
No. Each child has a one in two chance, whether the carrier is the mother or the father. The chance is the same for every pregnancy and does not change with how many children already carry it. A simple blood test gives each child a clear answer.
Why does an energy enzyme cause tumours?
Without the enzyme, fumarate builds up. At high levels it makes the cell act as if it is short of oxygen, so the cell switches on growth and draws in new blood vessels. The broad link is well studied, but not every detail is settled.
When should children be tested?
FH is one of the few adult cancer conditions where testing in childhood is usually offered. Kidney tumours have occasionally been found in children, so kidney scans often start from around the age of eight to ten. Your counsellor will discuss timing with you and your child.
My fibroid report says FH-deficient. What does that mean?
The pathologist found that the fibroid cells had lost the FH enzyme. That can happen by chance inside one fibroid, or it can point to an inherited fault. A blood test is the only way to tell the two apart, so ask your gynaecologist for a genetics referral.
We are a consanguineous family. Does that matter?
It matters in one situation. If both partners carry an FH fault, each pregnancy has a one in four chance of a child with fumarase deficiency, a severe illness from infancy. Marriage between relatives makes that more likely. A counsellor can test both partners before a pregnancy.
Where do we start?
Write down who in the family had kidney cancer, fibroids needing surgery young, or unusual skin bumps, and at roughly what age. Take that list to a genetic counsellor or your oncologist. Call the CION helpline if you are unsure who to approach, and someone will point you to the right clinic.
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) — FH Tumor Predisposition Syndrome
- MedlinePlus Genetics — FH gene
- MedlinePlus Genetics — Hereditary leiomyomatosis and renal cell cancer
- National Cancer Institute — Genetics of Kidney Cancer (Renal Cell Cancer) (PDQ)
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
FH mutation: which cancers and what riskWhat the kidney, skin and womb risks actually look likeSurveillance for FH carriersWhich checks carriers have, and from what ageFH and aggressive kidney cancerWhy this kidney tumour is never left to waitTesting the family for FHWho should be tested once a fault is found
Talk to us
Has someone in your family been told they carry an FH fault?
Tell us who was affected and how. We will help you find a genetic counsellor and work out who else in the family should be tested. One helpline serves every CION centre.