Hereditary hemorrhagic telangiectasia

Hereditary hemorrhagic telangiectasia (HHT) is an inherited disorder of the blood vessels that can cause excessive bleeding. People with HHT can develop abnormal blood vessels called arteriovenous malformations (AVMs) in several areas of the body. AVMs on the skin are called telangiectasias. AVMs can also develop in other parts of the body, including the brain, lungs, liver, or intestines.^[1] HHT is caused by a mutation in one of several genes, including ACVRL1, ENG, SMAD4, and GDF2. Changes in at least other two unknown genes are also suspected of causing HHT in some people.^[2] HHT is inherited in an autosomal dominant pattern, which means a person only needs to inherit one copy of the changed gene to have HHT.^[3] While there is no cure for HHT, treatment is symptomatic and supportive, with a focus on controlling bleeding and preventing medical complications, either through surgery or medication.^[1]

Although current treatment cannot stop telangiectasias or arteriovenous malformations (AVMs) from forming, many of the symptoms and complications associated with hereditary hemorrhagic telangiectasia (HHT) can be treated or prevented.^[4] Management of HHT includes checking for new or worsening AVMs and the treatment of complications such as nosebleeds, bleeding from the intestines or stomach, and anemia. Treatment of AVMs of the lung (pulmonary), brain (cerebral) and liver (hepatic) may also be recommended. ^[2][4]

Reducing the number and severity of nosebleeds can help prevent anemia. Treatment of nosebleeds may include using a vaporizer to increase the moisture of room air and keeping the inside of nose moist using nasal lubricants or sprays. Laser therapy may be used to remove the abnormal blood vessels (laser ablation). Other treatment may include medication or hormone therapy, but the effectiveness and safety of these treatments has not been established. If the nosebleeds continue despite other treatment, skin from a different part of the body may be grafted to replace the thin lining of the nose (septal dermoplasty) in an effort to cover and protect the fragile telangiectases.^[2][4]

Bleeding in the intestine or stomach is usually only treated if oral iron supplements cannot keep iron levels high enough to avoid anemia. Treatment may include surgical removal of AVMs or laser therapy to destroy and close the AVMs. If severe bleeding with uncontrolled anemia develops, treatment of AVMs in the stomach or intestine may include medication or hormone therapy, but the effectiveness and safety of these treatments has not been established. In addition to oral iron supplements, anemia may be treated by intravenous (IV) iron therapy or, in more severe cases, red blood cell transfusions.^[2][4] 

Treatment of AVMs of the lungs (pulmonary AVMs) is recommended if the person with HHT is having a hard time breathing (dyspnea), is unable to exercise without extreme fatigue (exercise intolerance), or has low blood oxygen levels (hypoxemia). Treatment of pulmonary AVMs may also be performed to prevent lung hemorrhage and the neurologic complications of brain abscesses and/or stroke. Treatment may include inserting a small inflated balloon or small metal coil in the artery that leads into the AVM in order to stop the blood flow through the AVM (embolotherapy) or surgical removal of the AVM.^[2][4] People with pulmonary AVMs are advised to take extra precautions to avoid serious complications. These recommendations include taking antibiotics before dental or surgical procedures, using special filters in IV lines to prevent even tiny air bubbles from entering the blood stream, avoiding blood thinners and non-steroidal anti-inflammatory drugs (such as aspirin, ibuprofin, and naproxen), and regular monitoring by a doctor familiar with HHT.^[4]

AVMs in the brain (cerebral AVMs) greater than 1.0 cm in diameter may be surgically removed. Alternative treatment includes inserting a small inflated balloon or glue-like substance to stop the blood flow through the artery involved in the AVM (embolotherapy) and/or using a narrow, focused beam of radiation to destroy the AVM (stereotactic radiosurgery).^[2][4]

AVMs in the liver (hepatic AVMs) are currently treated only if a person shows signs of heart failure or significant health problems related to the liver not working properly. Treatment might include standard heart failure medications, liver transplantation, or medications like bevacizumab.^[4]

In addition, guidelines for people with HHT recommend annual evaluations for anemia and neurologic conditions and re-evaluation for pulmonary AVMs every one to two years during childhood and every five years thereafter. Blood tests to check for anemia may be recommended more often depending on the frequency and severity of nose bleeds or if an intestinal or stomach AVM is bleeding. Women with HHT considering pregnancy are screened and treated for pulmonary AVMs; if pulmonary AVMs are discovered during pregnancy, they are treated during the second trimester.^[2]

The HHT Foundation recommends that people with HHT be assessed at least once at a specialized HHT Center. These centers facilitate the comprehensive coordination of care necessary for treating a patient who has HHT by proactively managing the care of patients with HHT. At these centers, a coordinated team of experts, knowledgeable about HHT, collectively cares for the patients seen at the Center. In most cases, a full-time nurse works closely with the specialists to care for the patient. Usually there is a coordinator on site to ensure proper follow up and coordination of patients care throughout the Center.^[5]

Each Center provides medical services that are currently being provided at that facility, but will provide these services in a more organized and consistent fashion. The patients have access to physicians who specialize in all aspects of HHT.^[5]

To locate an HHT Treatment Center near you, visit the following link:
http://www.hht.org/living-with-hht/treatment-centers/

If you are not able to get to a HHT Center, a genetics professional can help to coordinate your care. You may also benefit from seeing specialists in pulmonary medicine, gastroenterology, and an ears, nose and throat specialist (ENT). Other specialists may be appropriate, depending on your symptoms.^[5]

To find a medical professional who specializes in genetics, you can ask your doctor for a referral or you can search for one yourself. Online directories are provided by GeneTests, the American College of Medical Genetics, and the National Society of Genetic Counselors. If you need additional help, contact a GARD Information Specialist. You can also learn more about genetic consultations from Genetics Home Reference.