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Telomere biology genes: what they do and why they matter | CION Cancer Clinics
Telomere biology genes keep the protective caps on the ends of your chromosomes in good repair. When one of them is faulty, those caps wear down too fast, and the tissues that renew themselves most begin to fail, starting with the bone marrow. This page explains what telomeres are, what the main genes do, how the faults pass down families and why they raise the risk of certain cancers. 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 telomere biology genes do?
- Which genes are involved, and what does each one do?
- How does a telomere gene fault turn into illness?
- The words you will meet, in plain language
- How are these faults passed down a family?
- What this page cannot tell you
- Four things families tell us, and what is actually true
- Common questions about telomere biology genes
The short answer
What do the telomere biology genes do?
They keep the protective caps on the ends of your chromosomes in good repair. These caps are called telomeres. When one of these genes is faulty, the caps wear down too fast, and the tissues that renew themselves most begin to fail. That is why a single fault can affect the blood, lungs, liver, skin and mouth.
What a telomere is
Think of the plastic tip on a shoelace. It stops the lace fraying. Telomeres do the same job for chromosomes. Every time a cell divides, the tips get a little shorter. When they become too short, the cell stops dividing or dies. This is a normal part of ageing.
Why a fault causes illness
People with a telomere gene fault start life with shorter caps, or lose them faster. Tissues that must divide constantly run out of healthy cells first. The bone marrow is usually hit hardest, so blood counts fall. The lungs and liver can scar. Skin, nails and the lining of the mouth can change.
Why cancer risk goes up
When telomeres become very short, chromosome ends can break and stick together. Cells that survive this carry scrambled instructions, and some of them grow into cancer. The blood and the lining of the mouth and throat are the places this happens most.
This is a group of genes, not one. Your report will name the one that is faulty in your family.The genes, by job
Which genes are involved, and what does each one do?
More than a dozen genes are known. They fall into four teams, each with a different part of the work.
Building telomerase
Telomerase is the enzyme that adds length back to the caps. TERT makes its working part. TERC makes the template it copies from. A fault in either one weakens the whole enzyme. TERT faults are among the most common causes found in adults with inherited lung scarring.
Holding telomerase together
Several proteins keep telomerase stable and carry it to the chromosome ends. Without them, the enzyme falls apart or never arrives where it is needed.
Genes in this team
- DKC1, NOP10 and NHP2
- WRAP53, which delivers the enzyme
Guarding the cap
A group of proteins sits on the telomere and shields it, like a sleeve. TINF2 and ACD belong here. Faults in TINF2 often cause some of the most severe forms, starting in childhood.
Copying and untangling the end
The very end of a chromosome is hard to copy. RTEL1 untangles it so it can be copied, and CTC1, STN1 and PARN help finish the job cleanly. Some faults in this team cause illness only when both copies of the gene are affected.
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How does a telomere gene fault turn into illness?
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Born with shorter caps
Nothing shows at birth. The telomeres are simply shorter than they should be for the person's age, in every cell.
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The bone marrow wears out first
Blood cells are replaced constantly, so the marrow runs short of healthy cells early. Counts of red cells, white cells or platelets begin to fall.
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Outward signs may appear
Ridged or thin nails, patchy skin colour, white patches in the mouth and early greying hair. Many people have few or none of these.
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Other organs can follow
Scarring of the lungs and the liver can develop, often in adult life. Some people are first diagnosed through a lung clinic.
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Cancer risk climbs
Blood cancers such as MDS, a marrow disorder that can turn into leukaemia, and cancers of the mouth and throat become more likely than in other people the same age.
On your report
The words you will meet, in plain language
- Telomere
- The protective cap on the end of each chromosome. It shortens a little each time a cell divides.
- Telomerase
- The enzyme that rebuilds telomeres. Several of the genes on this page make parts of it.
- Telomere biology disorder
- The umbrella name for illness caused by a fault in any of these genes. Doctors often shorten it to TBD.
- Dyskeratosis congenita
- The classic, more severe form, usually recognised in childhood by nail, skin and mouth changes with low blood counts.
- Aplastic anaemia
- The bone marrow stops making enough blood cells of every kind. It is one of the commonest ways these disorders first show.
- Telomere length test
- A blood test, often called flow-FISH, that measures how long your telomeres are compared with others your age.
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Side by side
How are these faults passed down a family?
How it is passed on
What it means for the family
From one parent, as with TERT, TERC or TINF2
Each child has a one in two chance of inheriting it
From both parents, as with CTC1, NOP10 or NHP2
More likely when parents are related by blood
On the X chromosome, as with DKC1
Mostly affects boys; mothers usually carry it
New in the child
Common with TINF2; parents usually test negative
Across generations in one-parent families
Illness can start earlier in children than in parents
Being straight with you
What this page cannot tell you
It cannot tell you how a particular fault will behave in you. Two relatives with the same fault can have very different lives, one with marrow failure in childhood and another with mild lung changes in later life. What your specific variant means is a question for the counsellor or haematologist who ordered the test.
Who this does not apply to
Telomeres shorten with age, smoking and long illness in everyone. That is not a telomere biology disorder. Aplastic anaemia also has many other causes, and most people with it have no telomere gene fault.
A TERT change in a tumour is different
Many cancers, including some brain, bladder, thyroid and skin cancers, carry a TERT change that arose inside the tumour. It is not inherited and does not mean the family has a telomere disorder. That result belongs with your oncologist and the tumour testing pages.
Commonly believed
Four things families tell us, and what is actually true
"Short telomeres are just what happens with age."
Everyone's telomeres shorten, but a telomere disorder means they are far shorter than they should be for your age. The length test compares you with people the same age.
"It is a children's disease."
The classic form often shows in childhood, but many people are diagnosed as adults. Lung scarring or low blood counts in middle age can be the first sign.
"It only affects the blood."
The marrow is usually hit first, but the lungs, liver, skin and mouth can all be involved. Checks cover each of them, not just blood counts.
"A supplement can lengthen my telomeres and fix this."
No supplement has been shown to correct an inherited telomere fault. Some prescribed treatments can help blood counts, but only under a haematologist's close supervision.
Questions we are asked
Common questions about telomere biology genes
Which cancers are linked to telomere gene faults?
Mainly blood cancers, especially MDS and acute myeloid leukaemia, and squamous cancers of the mouth, tongue and throat. Cancers of the skin and the genital and anal area are also seen more often. The risk is well above that of other people the same age.
How is a telomere biology disorder diagnosed?
Usually with two tests together. A telomere length test shows whether the caps are very short for your age. A gene panel looks for a fault in the known genes. The two results are read side by side by a haematologist.
Can the fault be corrected?
No. A gene fault cannot be corrected or reversed. What can be treated is its effect. A stem cell transplant can replace failing bone marrow, and some medicines can raise blood counts for a time.
Why does it matter before a bone marrow transplant?
People with these faults react badly to strong conditioning treatment, so a gentler plan is used. Any brother or sister offered as a donor must be tested first, because a carrier sibling may look well but have weak marrow.
Does it matter that my parents are related?
It can. Some of these genes cause illness only when a faulty copy comes from each parent. Cousin or uncle-niece marriages, common in some Telangana families, make that more likely. Tell the counsellor, without embarrassment.
Should I avoid smoking and alcohol?
Yes. Tobacco in any form, including chewing, and alcohol both raise the risk of mouth and throat cancer, which is already higher. Smoking also damages the lungs, which may already be vulnerable.
Is this the same as Fanconi anaemia?
No. Both can cause bone marrow failure and raise cancer risk, but they come from different genes and are tested differently. Your haematologist may test for both when the cause of low blood counts is unclear.
Where do I start?
If you or a relative has unexplained low blood counts or early lung scarring, ask a haematologist whether a telomere length test makes sense. The CION helpline can 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) — Dyskeratosis Congenita and Related Telomere Biology Disorders
- MedlinePlus Genetics — Dyskeratosis congenita
- MedlinePlus Genetics — TERT gene
- MedlinePlus Genetics — Idiopathic pulmonary fibrosis
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
Telomere biology genes: which cancers and what riskThe cancers a fault raises the risk of, in detailShort telomere syndromes and cancer riskHow the named conditions differ from one anotherTelomere biology genes positive: what happens nextThe first checks and decisions after a positive resultTesting the family for telomere biology genesWho else should be tested, and why donors matter
Talk to us
Low blood counts nobody can explain?
A haematologist can tell you whether a telomere length test or gene panel is worth doing, and arrange counselling if a fault is found. One helpline serves every CION centre.