Hereditary Hemorrhagic Telangiectasia (HHT)

Hereditary Hemorrhagic Telangiectasia (HHT) is a genetic disorder that causes abnormalities of blood vessels. Also known as “Osler’s disease,” “Osler-Weber-Rendu disease”, and Osler-Weber-Rendu syndrome, HHT is an autosomal dominant genetic disorder that leads to vascular malformations. HHT is characterised by small vascular malformations, known as telangiectasia, on the skin and mucosal linings, nosebleeds, and arteriovenous malformations (AVMs) in various internal organs. Skin and mucosa telangiectasias are most remarkable on the tongue, hands/fingers, nose, lips, mouth/throat and conjunctiva.

The internal organs that can harbor AVMs often include the brain and lungs. In both, bleeding can seriously endanger life. Anemia may occur due to bleeding from digestive tract AVMs. High-output heart failure may develop in the presence of marked shunting arterial blood to the venous circulation, e.g. when AVMs are present in the liver.

Blood vessels are the tubes that carry blood around our bodies. There are two types of blood vessels: arteries and veins. Arteries carry blood under high pressure out to all areas of the body after being pumped by the heart. Veins carry blood that should be under low pressure, back to the heart. An artery does not usually connect directly to a vein. Usually there are very small blood vessels called capillaries that connect an artery to a vein.

A person with HHT has a tendency to form blood vessels that lack the capillaries between an artery and vein. This means that arterial blood under high pressure flows directly into a vein without first having to squeeze through the very small capillaries. This place where an artery is connected directly to a vein tends to be a fragile site that can rupture and result in bleeding. We usually call a blood vessel that is abnormal in this way a telangiectasia, if it involves small blood vessels. We tend to call it an arteriovenous malformation (AVM) if involves larger blood vessels. So, an AVM might be thought of as a big telangiectasia. The basic abnormality in the blood vessel is the same.

Telangiectases tend to occur at the surface of the body such as the skin and the mucous membrane that lines the nose. AVMs tend to occur in the internal organs of the body. The telangiectases (plural for telangiectasia) and AVMs of HHT occur primarily in the nose, skin of the face, hands, and mouth and the lining of the stomach and intestines (GI tract), lungs, liver and brain. It is not currently known why these abnormal blood vessels tend to occur in certain parts of the body and not others.

Although there is not yet a way to prevent the telangiectases or AVMs from occurring, most can be treated once they occur.

HHT Foundation International

Yale University School of Medicine
Dr. Robert I. White Jr., MD
Professor and Director, Vascular Malformation Group
Website: http://www.hhtavm.org

HHT occurs mainly in whites (1:5,000), more in certain areas of France, but much less in blacks (1 in 1 million). It is also seen with increased frequency in Mormon families from Utah.

Imaging of Hereditary hemorrhagic telangiectasia:

001
American Journal of Roentgenology

Exams and Tests

An experienced health care provider can detect telangiectases during a physical examination. There is often a family history of hereditary hemorrhagic telangiectasia.

Other signs include:

  • Chest x-ray may show a “spot on the lung” (arteriovenous malformation).
  • Echocardiogram may show heart failure.
  • Blood tests may reveal iron deficiency anemia.
  • Special blood gas tests may show decreased levels of oxygen in blood.
  • Endoscopy may show abnormal blood vessels that bleed easily in the throat, bowels, or airways.
  • Hepatomegaly may occur if there are abnormal blood vessels in the liver.

Genetic testing may be available for mutations in the endoglin or ALK1 genes. For more information, please visit http://www.geneclinics.org/profiles/hht/details.html (funded by the National Institutes of Health).

Nicole McConnell Foundation
Rainbows: Guiding Kids Through Life’s Storms

In the news:

Race for awareness of rare disease
Angela Carlisle-Brown and her husband, Greg Scot Brown, knew he had a medical condition when they married eight years ago. But research then had yet to conclude just how serious his condition was.

A bittersweet celebration
Playground will be dedicated to two volunteers, including PTO president whose life was cut short before she could see it built.

Notable Tweets:
@mars_beer Sadly this is true: One in five HHT patients will become disabled or die from the condition. http://www.hht.org/

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~ by marbleroad on May 17, 2009.

2 Responses to “Hereditary Hemorrhagic Telangiectasia (HHT)”

  1. Here is some additional information about the “genetics” of this condition that was written by our Genetic Counselor and other genetic professionals: http://www.accessdna.com/condition/Hereditary_Hemorrhagic_Telangiectasia/180. I hope it helps. Thanks, AccessDNA

  2. The web address for the HHT Foundation is http://www.hht.org
    This will put you in touch with all of the information about HHT, and ALL of the HHT Centers of Excellence worldwide!

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