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Hereditary hemorrhagic telangiectasia (HHT) is a genetic disorder that affects about one in 5000 people, or 1.4 million people worldwide. It causes improper connections between arteries and veins.
In people with HHT, some arteries may connect directly to veins instead of flowing through capillaries, thus forming telangiectasias or arteriovenous malformations.
Telangiectasias are malformations of small blood vessels in the skin, nose, stomach and intestines.
Arteriovenous malformations (AVMs) are abnormal connections in larger arteries or veins in the brain, spinal cord, lung and liver.
Complications of HHT result from the abnormal connection of the arteries and veins and include:
People with HHT inherit it in an autosomal dominant fashion. This means you get one “normal” gene copy from one parent and one mutated gene copy from the other parent. The abnormal, or mutated, gene creates a protein that is unable to perform its intended function in the cell and leads to abnormal blood vessel development.
Most often, people with HHT have a mutation either in one of three genes:
The mutated gene copy encodes a protein that is unable to perform its intended function in the cell.
It's rare — but not impossible — to develop HHT even if one of your parents does not have the disease.