What is HHT?

Understanding HHT

More than a nosebleed

What you need to know before exploring more about HHT is that if you are an individual looking for additional information or a clinician wanting to learn more for a patient we always recommend that you contact your national HHT Center of expertise for the best answers and care possible. If you are unable to reach or find a Center our National Member Organizations will be happy to assist you. If you have no HHT Organization in your country please contact HHT Europe and we will offer you all the necessary assistance.

Hereditary Haemorrhagic Telangiectasia is a rare genetic disorder of the blood vessels. It causes ArterioVenous Malformations (AVMs) in many vital organs.

What is an

AVM?

Arteries and Veins are connected by capillaries which filter the blood, allow oxygen exchange and lead to normal blood flow. In HHT patients, the capillary connection is often missing resulting in abnormal blood vessels (malformations). This gives rise to less filtering, faster blood circulation and less oxygen exchange, causing HHT symptoms.

Symptoms and obvious signs

Nosebleeds

90% of HHT patients suffer recurrent nosebleeds, which may result in anaemia and the need for
iron infusions and blood transfusions. These are small AVMs and appear like tiny red dots on the face, skin, lips, mouth and fingertips. (Other symptoms may include shortness of breath,
exercise intolerance, fatigue, migraine headaches, seizures, abdominal pain, intestinal bleeding)

Telangiectases

The manifestations of HHT are variable; patients can present with a varied combination of symptoms and signs.

The Silent Dangers

HHT

40% of patients have AVMs in the lungs and/or brain. These are the most dangerous manifestations of HHT because they may cause haemorrhage, strokes, or brain abscesses.
AVMs are often present in the gastrointestinal tract. They may bleed continuously, and are
difficult to locate and treat.

HHT Timeline

Screening for Pulmonary (lung) and Cerebral (brain) AVMs is essential to detect and treat when necessary and avoid a serious danger for patients during their entire life.

Newborns

Possible lung and brain AVMs at birth.

Age 12

Nosebleeds may begin. They can appear earlier, later or never at all.

Age 30 to 60

Telangiectases become more evident. Increase in nosebleeds. Possible increase in gastrointestinal bleeding.

Age 60+

Gastrointestinal bleeding may worsen. The dependence on iron infusions and blood transfusions may increase.

How is it

transmitted

HHT is an autosomal dominant hereditary disorder.
It does not depend on the sex of the child or the parent.
A parent with HHT may transmit the gene; each child of an affected parent has a 50% chance of inheriting the disorder. If you don’t have HHT you cannot pass it on.

Diagnosis

A diagnosis is likely if 3 of these clinical criteria are present:

Spontaneous & recurrent nosebleeds.
Multiple telangiectases in typical locations (face, lips, oral cavity, fingers)
AVMs in other organs (lungs, liver, brain, gastrointestinal tract)
A 1st degree relative with HHT by these criteria.

Prognosis

A cure does not exist but screening for manifestations in an HHT Specialist Center can help prevent the most serious complications of HHT.

1 in 5000 people worldwide have HHT

Figures

1 in 5000 people worldwide have HHT.
90% of them do not have a diagnosis.

Additional Resources

HHT International Guidelines (https://hhtguidelines.org)
VASCERN HHT WG resources (https://vascern.eu/expertise/rare-diseases-wgs/hht-wg/)