Hereditary hemorrhagic telangiectasia (HHT) is typically a hereditary or sometimes, de novo condition that affects the blood vessels. The condition is also known as Osler-Weber-Rendu syndrome. This disease usually results in repeated nosebleeds (epistaxis), sometimes responsible for anemia and the presence of small red spots on the skin (tongue, lips and fingers) called telangiectasia. This disease can also result in complications related to malformations of the vessels of the lung, liver, brain and spinal cord. These malformations can sometimes be responsible for serious and acute complications of the disease (i.e. brain abscess, stroke, bleeding, shortness of breath).
The hereditary condition is autosomal dominant, which means that if a person is known to have HHT, there is a 50% chance that first degree relatives such as parents, offspring or siblings may also have HHT. Approximately 1 in 5000 persons are affected by HHT.
Genetic variations, most commonly in two genes (ENG and ACVRL1) and more rarely in other genes (SMAD4 and GDF2), lead to abnormal blood vessel structures in those with HHT, from dilated micro-vessels (telangiectasia) to arteriovenous malformations (AVM).
Learn more about treatment of HHT at Boston Medical Center.
Conditions specific to HHT
Nosebleeds
One of the most common complaints of patients with HHT is nosebleeds, also called epistaxis. While bleeding tends to begin in the teenage years and is often only a mild inconvenience, it can also be a serious problem. Nosebleeds are almost universal in patients with HHT and can often progress to severe bleeding, leading to trips to the emergency room for packing or recurrent transfusions.
Treatment of epistaxis:
Often the first step in treatment of nosebleeds is providing humidification through topical saline application, humidifiers, and emollients in the nose (such as saline gel). For patients with more severe bleeding, other procedures can be used to manage the epistaxis. This can often be done in the otolaryngology office setting using minimally invasive lasers to ablate the telangiectasias.
Gastrointestinal bleeding
Telangiectases of the gastrointestinal tract are often present in HHT, and occur most commonly in the stomach and small intestine. These do not cause discomfort, but about 20-25% of HHT patients will develop symptoms of gastrointestinal bleeding, which can result in chronic anemia. In the absence of bleeding, these telangiectases are usually not treated.
Anemia
Because of recurrent or chronic blood loss, approximately 50% of patients with HHT have anemia due to iron deficiency. On initial consultation, your hematologist will evaluate you for iron deficiency and other causes of anemia to help determine your individualized treatment plan.
Assessment of bleeding risk (especially if anticoagulation or antiplatelet therapy is needed):
Therapeutic anticoagulation and antiplatelet therapy is tolerated by most patients with HHT who need it. However, your doctors may need you to see a hematologist to assess your bleeding risk and/ or modify your anticoagulation while optimizing medical treatment for your HHT.
References: blood.2020008739.pdf (silverchair.com), Hereditary Hemorrhagic Telangiectasia: Systemic Therapies, Guidelines, and an Evolving Standard of Care | Blood | American Society of Hematology (ashpublications.org), An International Multicenter Study of Intravenous Bevacizumab for the Treatment of Chronic Bleeding and Anemia in Hereditary Hemorrhagic Telangiectasia: The Inhibit-Bleed Study | Blood | American Society of Hematology (ashpublications.org)
Pulmonary AVMs
Pulmonary arteriovenous malformations (AVMs) occur in 15-50% of patients with HHT and can be associated with life threatening complications including massive hemoptysis, spontaneous hemothorax, stroke or transient ischemic attack related to paradoxical embolism and cerebral abscess. As many patients with pulmonary AVMs are asymptomatic prior to the development of severe complications, screening is recommended for all patients with HHT. Transthoracic echocardiography with agitated saline may be the screening test of choice but CT/Pulmonary angiograms are also utilized. Once identified, embolization of the affected vessels is the treatment of choice. These patients need long-term follow-up for detection of growth of untreated pulmonary AVMs and re-perfusion of those that have been treated. Patients require antibiotic prophylaxis for any procedure that may induce bacteremia.
Hepatic AVMs
Hepatic AVMs are common among HHT patients, but they are usually clinically silent, and rarely cause complications. For this reason, screening for hepatic AVMs is usually not performed in asymptomatic patients. Hepatic AVMs can cause asymptomatic elevation in liver enzymes, which are of little clinical importance, but can result in unnecessary diagnostic tests. Liver biopsy should be avoided.
In rare cases, diffuse hepatic AVMs can result in heart or liver failure. These patients may undergo intensive medical treatment, with liver transplantation considered for non-responders.
Cerebral AVMs
Arteriovenous malformations (AVMS) are tangles of dilated, thin-walled blood vessels that occur anywhere within the brain or on the dura mater (the covering of the brain). If an AVM ruptures, it can cause a stroke, brain damage, or death. AVMs occur in less than 1 percent of the population (300,000 Americans) and are more common in males than in females.
Skin telangiectasia
HHT may be diagnosed by a dermatologist when a patient has multiple telangiectasias on their skin and in the mouth. Telangiectasias are blood vessels at the top of the skin that are larger than normal, large enough to be seen as red dots or branching red lines without special imaging or magnification. When pressed firmly they may disappear, but the red color will reappear very quickly as blood flows back into that area. It is normal to have one or a few telangiectasias, usually on the cheeks or top of the hands, but when there are more than just a few, and especially when on the pink or red vermilion part of the lips and inside the mouth or nose, HHT should be considered. If you or a doctor notice many telangiectasias during a skin check, it is appropriate to look for other signs or proof of HHT. There are other genetic conditions that might cause an increase in fine blood vessels, especially in sun-exposed areas, so a dermatologist will look for or ask about other signs of HHT such as a history of frequent nosebleeds.
HHT telangiectasias can be treated with a pulsed dye laser, which targets blood vessels, or simple cautery. These procedures can be painful, so sensitive and younger patients may benefit from numbing anesthetic cream 30-120 minutes before the procedure. Treatment often requires more than one session.