Children's Hospital Colorado
Vascular Anomalies Center

Hereditary Hemorrhagic Telangiectasia

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What is hereditary hemorrhagic telangiectasia?

Hereditary hemorrhagic telangiectasia (HHT), also called Osler-Weber-Rendu disease, is a vascular condition that causes malformed blood vessels. Blood vessels (including arteries, veins and capillaries) are the tubes that carry blood through the body. Arteries move oxygen-rich blood from the heart out to the arms and legs. Veins move oxygen-poor blood back to the heart.

Normally, people have tiny capillaries that connect high-pressure blood in arteries to low-pressure blood in veins. Capillaries help decrease the pressure from arteries to veins. When someone has HHT, they can develop areas where blood flows directly from arteries to veins, skipping the capillaries. When arteries and veins form these direct connections, the malformation is called an arteriovenous malformation (AVM). AVMs are high-pressure, delicate connections that increase the risk of bleeding. AVMs may occur in many different organs in the body.

What causes HHT?

HHT is caused by genetic changes (mutations) that most often occur in one of three genes (ACVRL1, ENG and SMAD4). Three other genes have recently been reported to cause HHT-like disorders (GDF2, RASA1 and EPH4). About 10% to 15% of people with HHT will not have a change in any gene.

HHT is a dominant condition, which means that if a person has HHT, they have a 50% chance of passing it on to each of their children. It is very common for multiple family members to have the disease.

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