Tangling of abnormal blood vessels

Hereditary Hemorrhagic Telangiectasia (HHT) is also known as Osler-Weber-Rendu syndrome. It is a genetic (inherited) condition in which the normal fine capillary bed connecting arteries to veins is missing and instead an abnormal clump of larger fragile blood vessels is present. Small blood vessel clumps are called telangiectasia and larger ones in deep organs are called arteriovenous malformations or AVMs. These abnormal blood vessels can become dilated, bleed easily, and can cause life threatening hemorrhage (severe bleeding). This is how the disorder gets its name of Hereditary Hemorrhagic Telangiectasia.


It is a genetic disorder where a person inherited one mutated gene from one parent and one normal gene from the other parent. Parents with HHT have a 50% chance of passing on the abnormal gene to each of their children.

HHT affects approximately 1 in 5,000 people. Males and females from all racial and ethnic groups are affected equally.

Signs and symptoms

Most often, individuals will develop nosebleeds or visible red spots called telangiectasias on their skin. These appear as small red/purple pinpoint spots on the hands, face, mouth, and nose, with the numbers of spots increasing with age. Telangiectasia may not become visible or easily identified until someone has reached their 30's or 40's.

Patients can also develop a tangle of abnormal blood vessels called arteriovenous malformations (AVMs) in body organs such as the lungs, intestines, liver, brain and spine. These AVMs can rupture and may cause fatal bleeding into these vital organs. Although telangiectasias or AVMs cannot be prevented, they can be preventatively treated to avoid complications of bleeding and anemia from repeated episodes of blood loss. Younger family members should be screened to prevent such life-threatening bleeding.


Genetic testing can be used to diagnose HHT in almost 90% of people with the disorder. It may also be diagnosed by family history and the presence of symptoms.


Treatment of HHT depends on the parts of the body affected by the disorder. Treatment may include controlling bleeding from the nose and gastrointestinal (GI) tract and managing anemia caused by blood loss. AVMs that occur in the lungs and brain may require treatment to prevent complications.

Possible Complications

In addition to nose bleeding and bleeding from the telangiectasias of the skin (hands, face, mouth), there are other complications caused by these abnormal tangles of blood vessels.

  • Iron deficiency and anemia
    • Related to frequent blood loss
  • Shortness of breath, fatigue, and tiring easily with exercise
    • Related to anemia
    • Lung AVM
    • Liver AVM affecting the heart
    • Pulmonary hypertension (high blood pressure in the lungs)
  • Migraines and headaches
  • AVM in the brain
  • Seizure
    • AVM in the brain
    • Bleeding in the brain
    • Brain abscess
  • Stroke
    • Blood clot traveling from the lung AVM to the brain
  • GI Bleeding
    • AVM in the lining of the intestine
  • Back pain, swelling or numbness
    • AVM in the spine
  • Heart Failure
    • Extra blood flow to heart related to AVM in liver

how the ihtc can help you manage hht

The IHTC is committed to providing expert care for patients with HHT. As a center of excellence in the treatment of bleeding and clotting disorders, the IHTC offers a high level of coordinated care for patients with this disorder. We also provide prompt communication with your local healthcare provider related to our treatment plan and your progress. The IHTC team collaborates with national experts and patient participation in research studies may be available.

The IHTC recommends that you receive care at a specialized Comprehensive Care Facility such as the IHTC.

At the IHTC HHT Clinic we have an integrated team of healthcare providers with a specialist knowledge of, and research interest in HHT. A multidisciplinary approach is used for screening, diagnosis and management of HHT. Our health care team includes the following members

  • Pediatric and adult hematologists with specific knowledge of HHT who provide care for patients and their family members
  • Genetic counseling and testing
  • Screening for at-risk relatives
  • Management of complications such as nosebleeds and anemia
  • Access to onsite expert multidisciplinary team as needed: physical therapy, dietary, dental hygiene, social work, and academic/career counseling
  • Access to referral and care coordination with other needed specialists such as cardiology, pulmonology, neurology, gastroenterology, and interventional radiology

Learn more about our the IHTC's HHT clinic

For more information, please contact the IHTC.