Hereditary Hemorrhagic Telangiectasia (HHT)

Overview

Hereditary hemorrhagic telangiectasia, or HHT, is an inherited disorder that affects how blood vessels form. In people with HHT, some blood vessels develop abnormally, creating direct connections between arteries and veins that bypass the normal tiny vessels (capillaries) in between. These abnormal connections, called telangiectasias when small and arteriovenous malformations (AVMs) when larger, are fragile and prone to bleeding.

HHT is also known by the older name Osler-Weber-Rendu syndrome. It is passed down through families in an autosomal dominant pattern, meaning a child of an affected parent has a high chance of inheriting it. The most common and recognizable feature is frequent, spontaneous nosebleeds, but the condition can affect many parts of the body, including the skin, lungs, liver, brain, and digestive tract. Because some of these malformations can cause serious problems, awareness and screening within affected families are very important.

Symptoms

Symptoms vary widely, even among family members, but several features are characteristic of HHT.

• Frequent, spontaneous nosebleeds, often starting in childhood, which are the most common sign
• Small red or purplish spots (telangiectasias) on the face, lips, tongue, fingers, and inside the mouth
• Bleeding from the digestive tract, which may cause anemia, fatigue, or dark stools
• Anemia and tiredness from chronic blood loss

Larger malformations in internal organs may cause additional, sometimes serious problems. Lung AVMs can cause shortness of breath or allow clots and bacteria to bypass the lungs, while brain AVMs can rarely lead to bleeding or stroke. Many of these are silent until detected by screening.

Causes

HHT is caused by inherited changes (mutations) in specific genes that control the proper development of blood vessels. When these genes do not work correctly, vessels can form abnormal connections that lack the strength of normal capillaries.

• Genetic inheritance: the condition is passed down in an autosomal dominant pattern, so a single altered gene from one parent is enough to cause it.
• Family pattern: each child of an affected parent has about a 50 percent chance of inheriting the condition.

Because HHT is genetic, it is present from birth, though signs such as nosebleeds and skin spots often become more noticeable with age.

Risk Factors

The main risk factor for HHT is having a parent or close blood relative with the condition.

• A family history of HHT or of unexplained frequent nosebleeds and similar features
• Having a parent diagnosed with HHT, which carries roughly a 50 percent chance of inheritance
• Belonging to a family with known organ malformations linked to the disorder

HHT affects people of all backgrounds, and relatives of an affected person are encouraged to be evaluated even if they have few symptoms.

Diagnosis

HHT is often diagnosed based on characteristic features and family history, supported by tests to find malformations in internal organs.

• Clinical criteria: diagnosis considers frequent nosebleeds, telangiectasias, internal AVMs, and an affected family member.
• Genetic testing: can confirm the diagnosis and help test at-risk relatives.
• Imaging of the organs: screening for AVMs in the lungs (often with a bubble echocardiogram and CT), liver, and brain (with MRI).
• Endoscopy: to evaluate bleeding in the digestive tract.
• Blood tests: to check for anemia from chronic blood loss.

Because hidden organ malformations can be dangerous, screening is recommended even when someone feels well.

Treatment

There is no cure for HHT, but treatment effectively manages symptoms and prevents complications. Care is often coordinated at specialized centers.

• Nosebleed management: humidification, nasal moisturizers, and procedures such as laser treatment for stubborn or frequent bleeds.
• Treating organ AVMs: lung and brain malformations may be sealed off (embolized) by a specialist to prevent serious complications.
• Iron and transfusions: iron supplements and, when needed, blood transfusions to treat anemia from chronic bleeding.
• Managing gut bleeding: endoscopic treatments and medications in some cases.
• Preventive measures: precautions such as antibiotics before certain procedures for people with lung AVMs.

Regular monitoring helps detect and treat problems early.

Living With HHT

• Keep nasal passages moist with saline sprays or humidifiers to reduce nosebleeds
• Avoid blood-thinning medicines and NSAIDs unless approved by your clinician
• Take iron as prescribed to manage anemia
• Attend recommended screenings for lung, brain, and liver malformations
• Encourage at-risk relatives to be evaluated
• Carry information about your condition for emergencies and dental or surgical procedures

When to See a Doctor

See a clinician if you have very frequent nosebleeds, characteristic red skin spots, or a family history of HHT, so you can be evaluated and screened for organ involvement. Seek emergency care immediately for:

• A nosebleed that will not stop despite firm pressure
• Coughing up blood or sudden severe shortness of breath
• Sudden severe headache, weakness, vision changes, or trouble speaking (possible brain bleed or stroke)
• Vomiting blood or black, tarry stools
• Fainting or signs of significant blood loss

These can be life-threatening and require immediate medical attention.

Related Topics

Frequently Asked Questions

References

1. MedlinePlus, U.S. National Library of Medicine. Hereditary hemorrhagic telangiectasia.
2. National Organization for Rare Disorders (NORD). Hereditary Hemorrhagic Telangiectasia.
3. Cure HHT Foundation. About HHT.
4. National Heart, Lung, and Blood Institute (NHLBI). Arteriovenous malformations.