What is hereditary hemorrhagic telangiectasia (HHT)?

Hereditary hemorrhagic telangiectasia (HHT), also known as Osler-Weber-Rendu syndrome, is a genetic disorder that affects how blood vessels are formed. The blood vessels that form incorrectly are called telangiectases. These spots are prone to breaking open and bleeding. People with HHT often have nosebleeds (epistaxis) when younger. About 25% of these people later develop gastrointestinal bleeding.

Telangiectases that form in large blood vessels are called arteriovenous malformations (AVMs). AVMs lack capillaries and directly connect veins and arteries. These malformations can be very dangerous when found in the lungs (pulmonary AVMs or PAVMs), the liver, or in the brain.

Who gets hereditary hemorrhagic telangiectasia (HHT)?

HHT is a genetic disease. It is a “dominant” disorder, meaning that it is caused by one copy of one abnormal gene from one parent. If one parent has HHT there is 50% chance the child will get HHT. If your parents have HHT but you don’t, you cannot pass the gene onto your children or grandchildren.

How common is hereditary hemorrhagic telangiectasia (HHT)?

The incidence of HHT is hard to tell since there are such a wide variety of symptoms. It is known that HHT occurs in many ethnic groups. While many people go undiagnosed, there are currently about 500,000 people diagnosed with it around the world.

What causes hereditary hemorrhagic telangiectasia (HTT)?

HTT is caused by an abnormal gene on chromosome 9 or 12 is the cause of HHT. Individuals with this abnormal gene are not able to make the bodily substance that forms blood vessels.

What are the common signs and symptoms of hereditary hemorrhagic telangiectasia (HHT)?

Some commons signs of HHT include:

  • Reoccurring and frequent nosebleeds
  • Telangiectases that appear on the skins surface in your 30s and 40s
  • Black stools and anemia
  • Back pain and loss of feeling in the arms and legs

Telangiectases and arteriovenous malformations (AVMs) typically form:

  • In the nose
  • The lining of the stomach and intestines
  • Lungs
  • Liver
  • Brain
  • On the skin of the face, hands, and mouth

Last reviewed by a Cleveland Clinic medical professional on 10/28/2014.


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