About HHT

What is HHT?

Hereditary hemorrhagic telangiectasia (HHT) is a disorder of the blood vessels which causes bleeding in multiple organs of the body.

Diagram showing blood flow into an artery from the heart, through the capillaries, and into a vein

Normal blood flows from an artery, through capillaries, and into a vein. 

In normal blood flow, many tiny blood vessels called capillaries connect your arteries to your veins. Capillaries force the blood, which is under high pressure in an artery, to slow down before entering a narrower vein. People with HHT lack capillaries in certain key locations. Without these capillaries, blood flows directly from the artery to the vein, creating a fragile site—called a vascular malformation—that may bleed or result in other problems.

There are two types of vascular malformations caused by HHT:

  • Telangiectasias: small vascular malformations that appear as tiny red spots that are most often seen on the mouth, fingers, and face. Not all people with telangiectasia have HHT.
  • Arteriovenous malformations (AVMs): large vascular malformations that can occur in the liver, lungs, brain, and spine.

Vascular malformations due to HHT most often occur on the skin or in the nose but can form anywhere in the body. When they occur in vital organs such as the lungs, brain, liver, or digestive tract—where they can’t be seen—they can cause life-threatening complications.

There is no cure for HHT but with early diagnosis and proper treatment it can be managed. Many people with HHT lead long and healthy lives.

What causes HHT?

HHT is an inherited disease caused by a gene mutation. It is an autosomal dominant condition, which means that there is a 50 percent chance that you will have HHT if one of your parents has HHT and there is a 50 percent chance that you will pass the genetic mutation on to each of your offspring.

What are the symptoms of HHT?

HHT affects people in many different ways, making it difficult to diagnose. In some cases, symptoms do not appear until middle age or late in life, leading to a delay in diagnosis. The most common symptom of HHT is frequent nosebleeds.

Signs and symptoms of HHT include:

  • Nosebleeds, which often start in childhood
  • Telangiectasias (abnormal small blood vessels which appear as tiny red spots or vessels, usually on the mouth, fingers, and face)
  • Shortness of breath
  • Headaches
  • Seizures

Some symptoms of HHT do not have any effect on quality of life. In more extreme cases, the nosebleeds and telangiectasias can cause severe anemia. AVMs can also cause serious symptoms, such as bleeding, stroke, brain infection, shortness of breath, or heart failure.