HHT, also known as Osler-Rendu-Weber syndrome, is a genetic condition which affects the blood vessels. In HHT, there are abnormal connections between some blood vessels. HHT is characterized by one or more of the following:

About one in every 5,000 to 10,000 people have HHT. HHT is often under-diagnosed because people and doctors are not familiar with the symptoms.

HHT is most often diagnosed when the AVMs begin causing symptoms. A clinical diagnosis of HHT can be made if someone is known to have three of the four common signs:

  1. Frequent nosebleeds
  2. Telangiectasias found on the mouth, lips, tongue, and fingertips
  3. Internal AVMs found in the lungs, brain, liver, and intestines
  4. A family history of HHT

Nosebleeds are caused by telangiectasias in the nose. Almost all people with HHT will develop frequent nosebleeds not linked with trauma. Nosebleeds can occur as often as several times a day but are often less frequent. It is common for the nosebleeds to occur overnight for no reason. The chance of having nosebleeds increases with age.

Telangiectasias are most commonl on the lips, tongue, mouth, and fingertips. They are also seen on the fingers, ears, face, and chest. People with HHT usually have several to many telangiectasias. The chance to develop telangiectasias increases with age.

Internal AVMs cannot be seen on physical exam by a doctor so people with HHT may not know they have any. Imaging such as CT scans, MRIs and bubble echos are often needed to identify internal AVMs. Some people with internal AVMs will have signs of the AVM without knowing they have one. For example, a person with a lung AVM may have problems breathing and increased fatigue.