Frequently Asked Questions

What is HHT?

HHT is a genetic blood-vessel disorder – Full ‘Definition’ here. You and your family members who have HHT were born with it. In your family, your mom or dad, grandma or grandpa or other family members are likely to have HHT. You inherited HHT,  just like you inherited blue or brown eyes. People with HHT have blood vessels that developped abnormally and are called telangiectases and arteriovenous malformations (AVMs).

For more information see our Booklet Understanding HHT

What is different about my blood vessels?

Normal blood vessels: Everyone has blood vessels or tubes that carry blood to different parts of the body. These tubes are called arteries and the heart pumps fresh oxygenated blood into them and they carry the blood to your lungs, kidneys, liver, brain and other places in your body. Oxygen and nutrients are given to your body through small tubes called capillaries. Once the oxygen is gone, the blood returns to the heart in vessels called veins. Your blood continues this cycle all the time without you even realizing it!

HHT blood vessels: If you have HHT, some of your blood vessels are not normal and cause problems. In most people, arteries are connected to capillaries and then to veins and blood circulates throughout the body through these blood vessels or tubes. In the abnormal blood vessels or arteriovenous malformations (AVMs), the arteries are directly connected to the veins, making the vessels weak and sometimes they break and bleed. When these vessels break and bleed, they cause nose bleeds, red spots on your skin, problems with your lungs and sometimes your brain. The abnormal vessels that cause your nose to bleed and the red spots are called telangiectases. You may not have any red spots or nosebleeds now, but most likely you will sometime in your life. Almost everyone with HHT has nosebleeds and red spots on their skin. In addition to these two signs, abnormal vessels may develop in your lungs, liver and brain.

Is there a test for HHT?


Yes, genetic testing for HHT is available in Ireland, but it should be preceded by a clinical confirmation of HHT in your family.

The following Curaçao Diagnostic Criteria for HHT has been published by an international group of HHT experts. The diagnosis of HHT is considered definite if three or more of the following four criteria are present, or suspected if two of the following four criteria are present:

  • Spontaneous or recurrent nosebleeds
  • Multiple telangiectases in typical locations (Face Lips Oral cavity or Fingers)
  • AVMs in other organs (Lungs Liver Brain Gastro-Intestinal Tract)
  • A 1st degree relative with HHT by these criteria (Parent Sibling Grandparent)

You will be referred to your nearest HHT Specialist Centre for genetic testing.

How many people have HHT in Ireland?


Approximately 1 in 5000 people globally……. so it is estimated 1000 people here in Ireland.

How does HHT affect my lungs?


You breathe air into your body through your nose and mouth. The air goes down an air pipe in your throat to your lungs. Lungs work like big balloons. When you breathe in, your lungs expand and when you breathe out they get smaller. Your lungs put oxygen into your blood so your heart can pump it into your arteries. Arteries take fresh blood from your heart to your other organs and your veins carry the used blood back to your heart. For this to happen, you need capillaries to connect the arteries and veins. In HHT, the capillaries are missing or are not working properly in your lungs, which means your lungs can’t absorb as much oxygen as other people’s lungs. To get more oxygen, your lungs keep trying to get more air which makes you feel like you can’t catch your breath.

Why does HHT make me feel so tired?


Your body needs blood to do all of the things you like to do. Your body makes new blood all of the time but if you have lost some blood, through frequent nosebleeds for instance, you will feel weak until you have made enough new blood to replace the blood you lost. Sometimes people with HHT have to get extra blood through blood transfusions to help them feel better

What information will help me for my visit?

One of the most important things that you can do is to see your GP every year for a physical examination or check-up. If problems are identified, then recommendations can be made to see your HHT doctor. When you visit your HHT doctor, you may have some tests. These tests include a bubble echocardiogram (picture of your heart), chest CT scan (computerised tomography of chest), pulse oximetry (small device clipped to your finger)  and MRI of your brain (magnetic imaging of the brain). These tests help the doctors know and learn about your body and the blood vessels. They must know the size and location of the AVMs in order to make a decision about treatment. Doctors can treat these abnormal blood vessels in your nose, lungs and brain with a medicine, procedure or surgery. You will need to go to the hospital for treatment, some of which will be as an outpatient. You and your family are not the only ones who have HHT. Thousands of people have this condition. Many doctors and scientists are working hard to try to find medical treatments which make it easier for you to live with your HHT.

If I have frequent nosebleeds, do I have HHT?

Many people get nosebleeds and for lots of different reasons. So nosebleeds are an indication but not a confirmation of having HHT. Other indicators would be telangiectases or red spots on your skin

How can I manage my nosebleeds?

Nosebleeds are disturbing and awkward and can be socially embarrassing. However with practice and planning one can manage them quite well.

Read our leaflet “Coping with Nosebleeds” for practical information.

Does bleeding lead to anaemia?

Yes, frequent bleeding does lead to anaemia and HHT patients should be alert to this. One should get checked regularly by the GP who can prescribe suitable remedies.

Dr Adrian, I had CT scan about 3 years ago which identified small AVM’s. I had no symptoms at time. I have started to develop symptoms recently. I’m not due for a scan for 2 more years. Should I look for a scan sooner?

Depends hugely on what the symptoms are. We would need to look back at individual record to check the AVMs you had, how small they were,  and know what your individual symptoms are. Those symptoms might have nothing to do with PAVMs, or they might.

Dr Adrian, Do you recommend any preventative treatments for migraines as a result of HHT and is it possible to get migraines from HHT?

No and no, is answer. Firstly the treatment for migraine, whether it’s related to HHT or not, will be the same. So I would advise you consult your own Dr or neurologist to manage that, and ask their advice. It’s not that the migraines one gets from HHT are qualitatively different from those migraines of someone who doesn’t have HHT might suffer from, its simply that the risk of you’re having it goes up a little bit. We know the bio-chemical reason for that and we can go into the science behind it, but it has to do with certain chemicals not being processed in the lungs and passing thru the AVMs. So the way migraine is treated is the same whether you have HHT or not.

But if you have HHT statistically, you are at a greater risk of suffering from migraines and we know from the literature that managing PAVMs (managing them if they’re big enough) can reduce that risk to that of the general population. There isn’t a preventative treatment that is specific to HHT people nor is there any screening test for migraines related to HHT….. just an association!

Does Dr Brady or his team have a list of HHT Specialists that he can share with us?

Depends on what your manifestation is. We don’t keep list of people who are in/out! The ENT surgeons interestingly are very commonly the first people who see patients with HHT because the first manifestation that people become aware of and seek medical attention for would often be nosebleeds. So ENT surgeons are probably most plugged into this diagnosis but are often focused on the nosebleeds aspect of it. What we are trying to do all the time is increase awareness of the bits that are more dangerous, that we need to screen for. We don’t keep a specific list of specialists but we are aware of people who have interests in HHT manifestations in their own particular specialty and we do link in with them for specific patients as necessary.

For more info – go to

Dr Adrian, is it ok to exercise with small PAVMs?

Absolutely! Most people who have HHT and have small PAVMs should not restrict their life – other than NOT scuba-diving in any way! You don’t have to protect yourself by not exercising aggressively or doing whatever you want to do. You’re not going to increase your risk of an unfortunate or unpleasant event by taking exercise. Don’t wrap yourself in cotton wool essentially. If you have very large PAVMs reducing your exercise capacity, then obviously we want to know about you and we will do our best to help you. But small PAVMs – live a normal life!

What is Dr Adrian’s advice to his patients with regards to screening of any possible Brain AVMs? Is it necessary to repeat AFTER an initial negative result? Can CAVMs grow after a negative screening result?

To the best of our knowledge, they do not. We rely on international literature & research that’s been done over the years and that would all support the single screening brain strategy that we use. It seems that these are either present or not present. PAVMs are a little bit different. They DO tend to grow with time but to the best of our knowledge CAVMs do not appear, having been absent on an initial screening test.

I’m having severe reactions to Iron infusions… are there any other options or something to help with symptoms…it’s severe joint pains , back pain sweats, shivers & sickness for 5 days. Any advice?

Best to discuss with clinician managing these iron infusions.

Dr Adrian, How can our families help our GPs to recognise and diagnose HHT? Where should we refer them onto?

We rely heavily on family practitioners to help us with referrals and to triage people. A lot of people who have nosebleeds for example and are aware of HHT would be interested in knowing whether they might be related.  We fall back on the clinical criteria – the 4 diagnostic “Curacao Criteria” – for making a clinical diagnosis of HHT.  We have information – brochures that we produced many years ago – that we can make available to GPs. All of this information is available on

If you’re worried about it, I would say talk to your GP, bring any information you may have gleaned from the website to them, let them consider with you whether or not you fit the clinical criteria. If they think you do, then referral to our Centre for screening in Cork would be what we would advise.

Dr Adrian, has anyone ever tested positive for more than one of these genes?

Not that I’m aware of. I can imagine it might have happened but on a statistical basis, it would be extraordinary to have more than one of the mutations that affect the same common pathway. But I’m sure it can happen – statistically anything can happen!

Dr Adrian, is it safe for a HHT patient who has had a TIA (Blood Clot) and has a CAVM to take the Astra Zeneka vaccine? Given the treatment for blood clots which can cause increased frequency & severity of nosebleeds, does this cause Dr Brady to consider the vaccines implicated in blood clots should be avoided by HHT patients?

 I’m not surprised that there are lots of questions about vaccines and the blood clotting concerns that have been raised in the literature. The answer is NO! There was some interesting advice that I saw only yesterday (23/4/21) that emerged from NIAC which is distilling all the international research that is presently available on this. It essentially says that if you  had the common type of blood clot that patients often experience  – a DVT in the leg or a Pulmonary Embolism (little bit less common) – that doesn’t mean you’re at an increased risk of the dangerous clots that are associated with the Adenovirus-type vaccines. There’s no statistical association. So if you’ve had a DVT, for whatever reason, ( common reason would be someone whose had immobilisation; or maybe a long international flight; there’s increased incidence in women on the oral contraceptive pill) those people have statistically a higher risk of having these very specific types of clots that are associated with Adenovirus-type vaccines. And those are Cerebral Venous Sinus Thrombosis (a clot in a vein in the brain) or Splanchnic Vein Thrombosis (a clot in the veins that drain from your gut).

So there’s no increased risk for these people.

My father and my son have frequent nosebleeds. Is there a connection?

There may very well be a connection if a father & son both experience nosebleeds. HHT is a rare genetic disorder of the blood-vessels, which can cause unexpected & recurrent nosebleeds. 

I suffer from chronic fatigue and migraines, other family members have similar symptoms. Is there a common cause?

There may very well be a cause for your chronic fatigue and migraines – if you have HHT.  HHT is a rare genetic disorder of the blood-vessels, which can cause chronic fatigue & migraines if present in the lungs or brain. 

What causes nosebleeds?

 Some nosebleeds can be as a result of having HHT. HHT is a rare genetic disorder of the blood-vessels, which can cause unexpected & recurrent nosebleeds.

When should you worry about a nosebleed?

You should worry about a nosebleed if it lasts more than 15mns and/or if they appear unexpectedly and recurrently.  If you come from a family who suffer nosebleeds, you should consider investigating if you indeed have the HHT gene. Follow up with a HHT expert at the National HHT centre, Mercy University Hospital, Cork.

Does stress cause nose-bleeding?

Stress can cause nosebleeds especially if you have HHT.  HHT is a rare genetic disorder of the blood-vessels, which can cause unexpected & recurrent nosebleeds

What are the common causes of nosebleeds?

A head cold or high blood pressure can cause nosebleeds. However HHT, which is a rare genetic disorder of the blood-vessels, can cause unexpected & recurrent nosebleeds.

What are nosebleeds a sign of?

Unexpected and recurrent nosebleeds can be a sign of HHT. 90% of HHT patients experience nosebleeds

Frequent nosebleeds.

HHT is a rare genetic disorder of the blood-vessels, which can cause unexpected & recurrent nosebleeds

I’m having occasional bleeds from my tongue. My mother had nosebleeds. Could there be a connection?

HHT is a rare genetic blood-vessel disorder and can present with telangiectases on the lips, face, skin, tongue amongst some places. Telangiectases are tiny blood vessels and when they rupture they can bleed. 

Why are my nosebleeds getting more severe as I get older?

For people with HHT, nosebleeds can become more frequent & heavier as they age.

Why is my teenage son, who appears to be healthy, so breathless and fatigued after any exercise?

HHT is a rare genetic blood-vessel disorder and can present in the lungs. Up to 40% of HHT sufferers experience symptoms such as breathlessness , fatigue, migraine, dizziness

Should I take iron if I suffer from frequent heavy nosebleeds?

Iron is a great way to manage your blood count levels if you suffer from nosebleeds. However if you suffer from recurrent nosebleeds you should investigate if you could possibly have HHT. 

Is transfusion the best treatment for anaemia?

If you develop anaemia, you should take the advice of your Health provider. However you should investigate the cause of your anaemia and consider if HHT could possibly be the cause.

What is the relationship between iron levels and ferritin?


Haemoglobin is the iron/oxygen part of red blood cells that carries oxygen through your body. When we lose blood, we lose a lot of this and your body has to make more haemoglobin.
Your body makes haemoglobin by grabbing iron and binding it to oxygen. When you increase your haemoglobin during this process, your iron counts will drop, so you need to find more iron.
Ferritin is a protein that stores iron. When your haemoglobin decreases and your iron counts decrease, your body will grab iron from your stores to make more haemoglobin. After this process, you need to ingest more iron through food, supplements, or IV.
Iron will typically stay in the “normal” range for most people unless you’re out of ferritin. Hence the reason to keep ferritin above 100 for HHT patients.