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SMAD4 and hereditary haemorrhagic telangiectasia | CION Cancer Clinics
A SMAD4 fault can cause hereditary haemorrhagic telangiectasia, or HHT, as well as polyps in the gut. HHT is a condition of fragile blood vessels that causes nosebleeds and, more importantly, hidden vessel problems in the lungs, brain or liver. This page explains what HHT is, why every SMAD4 carrier is checked for it, what the checks involve and which symptoms need same-day care. 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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The short answer
What does SMAD4 have to do with HHT?
A fault in SMAD4 can cause two conditions at once. One is juvenile polyposis, which causes polyps in the gut. The other is hereditary haemorrhagic telangiectasia, or HHT, a condition of fragile, abnormally formed blood vessels. Many SMAD4 carriers have at least some features of HHT, so every SMAD4 carrier is checked for it, even if they have never had a nosebleed. BMPR1A carriers do not need these checks.
What HHT actually is
In HHT, some small blood vessels form without the normal thin network between artery and vein. On the skin and in the nose these appear as tiny red spots called telangiectasias, which bleed easily. Deeper inside the body, larger tangles called AVMs can form in the lungs, liver or brain. The name simply describes this: hereditary means inherited, haemorrhagic means bleeding, and telangiectasia is the red spot.
Why it matters even without symptoms
An AVM in the lung often causes no symptoms at all. It can still let small clots or germs slip past the lung's natural filter and reach the brain, causing a stroke or an abscess. A simple test can find these AVMs, and they can usually be closed off before they cause harm.
Repeated nosebleeds in a child are often put down to the heat, and a low haemoglobin to diet. In a SMAD4 family, both deserve a proper look, because together they can be the first clue to HHT.
Checking for HHT is about prevention. Most of what it finds can be treated or watched safely.Four places to watch
Where in the body does HHT show up?
Not everyone with SMAD4 has every feature. Some have only one, and some have none that can be seen.
Nose, skin and mouth
Repeated nosebleeds are the most common sign, often starting in childhood. Small red spots may appear on the lips, tongue, face or fingertips, usually later in life.
Often noticed as
- Nosebleeds without an obvious cause
- Red spots that fade briefly when pressed
- Blood on the pillow in the morning
The gut
Fragile vessels in the stomach and bowel can bleed slowly. With SMAD4, this adds to the bleeding that polyps can cause, so a low haemoglobin and tiredness are common and are checked for with a simple blood count.
The lungs
Lung AVMs are the most important finding to look for. They may cause breathlessness, low oxygen or blue-tinged lips, but many cause nothing at all until a clot or an infection passes through them.
This is why the lung check is done even when you feel well.Brain and liver
AVMs in the brain are less common but can bleed. Some programmes offer a brain MRI, particularly for children. Liver AVMs are frequent in HHT but usually need no treatment, only awareness. They matter mainly because a liver biopsy should then be avoided.
Not sure whether this applies to you?
Ask an oncologistThe HHT check-up
How is a SMAD4 carrier checked for HHT?
Questions and an examination
The doctor asks about nosebleeds, breathlessness, headaches and bleeding in the family, and looks at the nose, lips, tongue and hands for red spots.
A bubble test of the heart and lungs
An ultrasound of the heart is done while harmless tiny bubbles are injected into a vein. If bubbles reach the left side of the heart, a lung AVM may be present, and a CT scan of the chest follows.
A blood count and iron check
This shows whether hidden bleeding from the nose or gut is lowering the haemoglobin. Iron tablets or infusions can correct it.
Brain and heart scans where advised
Some teams add a brain MRI. Because a widened main artery has been reported in some SMAD4 carriers, a heart ultrasound may also be offered.
On your report
The words you will meet, in plain language
- HHT
- Hereditary haemorrhagic telangiectasia. An inherited condition of fragile, abnormally formed blood vessels.
- Telangiectasia
- A small widened blood vessel near the surface, seen as a red spot. It bleeds easily because its wall is thin.
- AVM
- Arteriovenous malformation. A tangle where an artery joins a vein directly, skipping the fine vessels that normally sit between them.
- Bubble echo
- A heart ultrasound done with tiny bubbles in a drip, used to look for a lung AVM without radiation.
- Embolisation
- A procedure that blocks off an AVM from inside the blood vessel, using a thin tube passed from the groin or arm.
- JP-HHT
- The combined condition of juvenile polyposis and HHT, caused by a SMAD4 fault.
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Signs that cannot wait
If someone with SMAD4 or HHT has a sudden severe headache, weakness or numbness on one side, slurred speech, a fit, sudden breathlessness or is coughing up blood, go to the nearest emergency department the same day. Tell the staff they have HHT, because it changes how they are investigated. A nosebleed that will not stop despite firm pressure also needs urgent care.
Being straight with you
What this page cannot tell you
It cannot tell you whether you have HHT features or how serious they might be. That depends on the checks above and on your own history. SMAD4-related HHT is rare, studies so far are small, and very little of the data comes from Indian families. It also cannot tell you whether an AVM that has been found needs treatment now or can simply be watched. That depends on its size and on scans your team will review with you.
It cannot read your result
What your specific variant means is a question for the counsellor who ordered the test. A variant of uncertain significance, a change nobody can yet call harmful or harmless, is not a confirmed fault and should not start HHT screening on its own.
Who this does not apply to
BMPR1A carriers do not have a raised risk of HHT. Most people with occasional nosebleeds do not have HHT and do not need this test. HHT is more often caused by other genes, which carry no polyp risk, so a family with HHT alone will be guided by a different plan.
Commonly believed
Four things families believe about HHT, and what is true
"No nosebleeds, so no HHT."
Some SMAD4 carriers have lung or other AVMs without any nosebleeds. The screening tests are offered precisely because the most important features can be silent.
"Nosebleeds are just the heat."
Hot, dry weather can make nosebleeds worse, but repeated nosebleeds in a SMAD4 family deserve a proper check. They are often the first visible sign of HHT.
"A lung AVM means major surgery."
Most lung AVMs are closed off by embolisation, a procedure done through a thin tube in a blood vessel. It does not usually need open surgery.
"HHT is a cancer."
It is not. HHT is a blood vessel condition. The cancer risk with SMAD4 comes from the polyps in the gut, which are watched separately.
Questions we are asked
Common questions about SMAD4 and HHT
Does every SMAD4 carrier have HHT?
Not every carrier, but many have at least some features, and some have features that cannot be seen or felt. That is why every SMAD4 carrier is offered HHT checks, including a lung test, rather than waiting for symptoms to appear.
When should children be checked for HHT?
Usually once the SMAD4 result is known, including in childhood. Lung AVMs can be present in children, and finding them early allows treatment before any complication. Your counsellor will explain which checks suit your child's age.
Do I need antibiotics before dental work?
If you have a lung AVM, or have not yet been checked, many HHT specialists advise antibiotics before dental treatment to protect against a brain abscess. Ask your team whether this applies to you and tell your dentist about the condition.
Is pregnancy safe with SMAD4 and HHT?
Most women with HHT have safe pregnancies, but pregnancy can make lung AVMs grow. Ideally, lung screening is done before pregnancy, and the pregnancy is looked after by a team that knows about HHT.
How are nosebleeds managed?
Keeping the inside of the nose moist with a suitable ointment or spray helps many people. If bleeding is frequent, an ENT surgeon can treat the vessels directly, and tablets that help blood clot are sometimes used. Iron replaces what is lost.
Does HHT change how the bowel is checked?
The colonoscopy and stomach endoscopy still go ahead as planned. The team simply knows that some bleeding may come from fragile vessels rather than polyps, and may treat those vessels during the same procedure.
Should my relatives be tested?
Yes. Once a SMAD4 fault is known, parents, brothers, sisters and children can be tested for that exact change. Those who do not carry it need neither polyp screening nor HHT checks. A counsellor can help you plan who to approach first.
Where can we get these checks in Hyderabad?
Start with a genetic counsellor or your gastroenterologist, who can coordinate the heart, lung and blood tests. Call the CION helpline if you are unsure who to approach, and someone will point you to the right clinic. Bring any reports you have.
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) — Hereditary Hemorrhagic Telangiectasia
- GeneReviews (NCBI) — Juvenile Polyposis Syndrome
- MedlinePlus Genetics — Hereditary hemorrhagic telangiectasia
- MedlinePlus Genetics — SMAD4 gene
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
SMAD4 and BMPR1A cancer risksThe bowel and stomach risks that come with the same faultSurveillance for SMAD4 and BMPR1A carriersHow HHT checks fit alongside bowel screeningWhich gene causes which patternWhy SMAD4 and BMPR1A families are managed differentlyTesting the family for SMAD4 and BMPR1AWho to test next, and in what order
Talk to us
Do you carry SMAD4 and have not been checked for HHT?
Tell us your result and which checks you have already had. We will help you arrange the lung, heart and blood tests alongside your bowel surveillance. One helpline serves every CION centre.