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Hereditary hemorrhagic telangiectasia (HHT) is a rare, genetic condition. It affects the way blood vessels form and can create problems with how they operate and interact with each other. In particular, some blood vessels in a person with HHT do not possess the needed connections of capillaries between arteries and veins. This lack of connection creates high-pressure bloodflow between veins and arteries resulting in fragility of the veins at the artery/vein connection site that can create bleeding or hemorrhage.
Absence of capillary connection in hereditary hemorrhagic telangiectasia does not occur in all vein/artery connections. Yet it can occur in different areas of the body and affect small or large arteries and veins. Size of vessels determines whether the delicate and prone to bleeding connection is referred to as a telangiectasia or an arteriovenous malformation. The latter may be more dangerous and located in areas like the lungs or brain, posing significant threat if bleeding begins to occur. Many telangiectases are present near the skin or near the mucous membranes and one hallmark of this condition is frequent nosebleeds, or visible evidence of telangiectases on the skin.
There are several different types of hereditary hemorrhagic telangiectasia, which can vary in severity. One kind, called juvenile HHT has an additional feature. People may be prone to developing polyps in their intestinal tract in addition to having these capillary-absent venous connections.
All kinds of this condition are inherited. Pattern of inheritance is autosomal dominant, which means people need only inherit a single gene from a single parent in order for the disease to be expressed. This also means people with HHT have a 50% chance of passing the condition on to any progeny.
Some of the most common symptoms of HHT include nosebleeds, which may occur often, and presence of purple or red spots (telangiectases) on the face or skin by mid-life. People may also exhibit bleeding in other places where the matter is more serious. Stomach, liver, brain, or lung bleeds can occur, and identifying that a person has hereditary hemorrhagic telangiectasia is important so these potential risks can be monitored. If bleeding is occurring regularly, but is not severe, some people become anemic and blood tests might be performed often to look for this sign.
It’s important to note that symptom expression varies greatly and many symptoms can be controlled or medically managed. For instance, using humidity at home can help with frequent nosebleeds. Unsightly or bothersome telangiectases can be surgically removed. A number of surgical interventions are useful in correcting arteriovenous malformations so severe bleeding does not occur internally. People with HHT do need careful monitoring by a specialist, but many can live very normal lives with very few interventions.
One thing that all people with hereditary hemorrhagic telangiectasia do tend to require is bacterial endocarditis (BE) prophylaxis. This is antibiotic treatment taken prior to dental procedures. Weakness in the mucus membranes in the mouth creates greater likelihood of bacteria entering the bloodstream, which can cause infection in the heart. Anyone with HHT should inform dentists to be certain this precaution is observed, even for simple things like teeth cleanings.