Blood Disorders

Facts About Hereditary Hemorrhagic Telangiectasia (HHT)

HHT is a disorder in which some blood vessels do not develop properly. A person with HHT may form blood vessels without the capillaries (tiny blood vessels that pass blood from arteries to veins) that are usually present between arteries and veins. The space between an artery and a vein is often fragile and can burst and bleed much more easily than other blood vessels. Men, women, and children from all racial and ethnic groups can be affected by HHT and experience the problems associated with this disorder, some of which are serious and potentially life-threatening. Fortunately, if HHT is discovered early, effective treatments are available. However, there is no cure for HHT.

Signs

Nosebleeds are the most common sign of HHT, resulting from small abnormal blood vessels within the inside layer of the nose. Abnormal blood vessels in the skin can appear on the hands, fingertips, face, lips, lining of the mouth, and nose as delicate red or purplish spots that lighten briefly when touched. Bleeding within the stomach or intestines is another possible indicator of HHT that occurs because of abnormal blood vessels lining the digestive tract. Additional signs of HHT include abnormal artery-vein connections within the brain, lungs, and liver, which often do not display any warning signs before rupturing.

Causes of HHT

HHT is a genetic disorder. Each person with HHT has one gene that is altered (mutated), which causes HHT, as well as one normal gene. It takes only one mutant gene to cause HHT. When someone with HHT has children, each child has a 50% chance to receive the mutant gene from his/her parent, and therefore to have HHT, as well. Each child also has a 50% chance to receive the normal gene and not be affected with HHT. At least five different genes can cause HHT, three of which are known.

Diagnosis

HHT can be diagnosed by performing genetic testing. Genetic testing can detect a gene mutation in about ¾ of families with signs of HHT, which if found can establish the diagnosis of HHT in individuals and families who are unsure about whether they have HHT. HHT can also be diagnosed by using clinical criteria (presence of signs and a history of signs in a parent, sibling, or child).

Complications and Treatments

The complications of HHT can vary widely, even among people affected by HHT in the same family. Complications and treatment of HHT depend on the parts of the body that are affected by this disorder. Treatment may include controlling bleeding and anemia and preventing complications from abnormal artery-vein connections in the lungs and brain.