Hereditary hemorrhagic telangiectasia

Chest | Hematology | Hereditary hemorrhagic telangiectasia (Disease)


Hereditary hemorrhagic telangiectasia is a disorder that results in the development of multiple abnormalities in the blood vessels.

In the circulatory system, blood carrying oxygen from the lungs is normally pumped by the heart into the arteries at high pressure. The pressure allows the blood to make its way through the arteries to the smaller vessels (arterioles and capillaries) that supply oxygen to the bodys tissues. By the time blood reaches the capillaries, the pressure is much lower. The blood then proceeds from the capillaries into veins, through which it eventually returns to the heart.

Causes and Risk factors

In hereditary hemorrhagic telangiectasia, some arterial vessels flow directly into veins rather than into the capillaries. These abnormalities are called arteriovenous malformations. When they occur in vessels near the surface of the skin, where they are visible as red markings, they are known as telangiectases (the singular is telangiectasia).

HHT is caused by defects in at least 3 genes, but only one abnormal gene is the cause in one family. The abnormal gene found on Chromosome 9 is called endoglin and causes HHT1.

Diagnosis and Treatment

HHT can be diagnosed through genetic testing and/or by clinical criteria (the Curacao Criteria). Treatment of a person’s HHT depends on which parts of the body are affected. Some aspects (nosebleeds) are treated symptomatically, whereas as others are treated preventatively (lung and brain AVMs).

Treatments for nosebleeds can range from lubrication of the nasal mucosa, laser therapy and septal dermoplasty for severe transfusion dependent patients. Telangiectases of the skin can be treated with laser therapy. Lung and brain AVMs should be treated before they cause complications. Lung AVMs can almost always be treated completely with embolization, a high-tech low-risk procedure.

Bleeding from the stomach or intestines is generally treated only if it causes anemia (low blood count). Iron replacement therapy is the first line of defense. Liver AVMs are currently treated only if a person shows signs of liver or heart failure as a result of a liver AVM. ...