Hereditary Hemorrhagic Telangiectasia (HHT) is a hereditary disorder that affects blood vessel development in many parts of the body. The arteries and veins are directly joined without the normal collection of capillaries between them. These abnormalities range from small lesions to larger ones. The most commonly affected organs are the nose, skin, lungs, gastrointestinal tract, and brain, in that order.
HHT is an autosomal dominant genetic disorder, meaning that an affected individual only needs to have one copy of the abnormal gene, and only one of the two parents needs to have the gene. (In contrast, cystic fibrosis requires two copies of the abnormal gene, and both parents must have and contribute one.) Both men and women can be affected. As a result, approximately half the children of an adult with HHT will also have HHT.
The genetic basis of HHT is becoming better understood through the efforts of clinicians and scientists. Genetic testing is now available thanks to the HHT Foundation International and individual leaders at several HHT centers.
Because HHT can result from many different mutations in at least three different genes, genetic testing is not perfect in identifying the responsible mutation in every family. The diagnosis of HHT should first be confirmed in at least one member of a family based on symptoms and family history. This family member should be tested first to see if the genetic mutation causing HHT can be detected using currently available techniques.
Depending on the test result, a physician can determine whether testing blood samples from additional family members will be helpful. A UT Southwestern Medical Center geneticist can help you and your family members understand the various options.
At UT Southwestern, our medical screening protocol is aimed at detecting internal arteriovenous malformations (AVMs) before they cause major medical problems. All direct family members of a family with HHT should be screened, as there is no relationship between severity of nosebleeds or the number of skin and mucous membrane telangiectasia and the degree of internal involvement.
Because pulmonary AVMs may cause severe complications even if asymptomatic, we use a saline contrast echocardiogram (“bubble echo”) to screen for their presense. If bubbles go from the right to the left side of the heart, there are at least some abnormal blood vessels in the lungs. If positive, we follow with a CT scan to localize the AVMs and plan treatment.
We screen for cerebral AVMs using cerebral MRI. We also screen for anemia with a blood count, and screen for symptoms and signs of other organ involvement. Because there is currently no treatment that affects the development of intestinal or liver AVMs, we do not perform screening procedures. We begin treatment when symptoms develop.
The UT Southwestern Hereditary Hemorrhagic Telangiectasia Center is a team of experienced professionals assembled in response to a regional need for the highest quality HHT care.
Our physicians are experts in HHT treatment and preventative options. If specific problems such as severe nosebleeds, GI bleeding, pulmonary, or neurological symptoms are identified, consultations with various specialists can be arranged during the same visit.