Hereditary Hemorrhagic Telangiectasia (HHT): Disease

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Hereditary hemorrhagic telangiectasia (HHT), also called Osler-Weber-Rendu syndrome, is a genetic disorder that affects blood vessel formation. People with HHT develop small lesions called telangiectases, which can burst and bleed. Frequent nosebleeds are common, but telangiectases in other areas of your body can cause serious complications. Early treatment can prevent life-threatening complications.

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Hereditary hemorrhagic telangiectasia (tuh-lan-jee-uk-TAY-zhuh) or HHT is a rare, inherited genetic disorder that affects how your blood vessels form. Your circulatory system is a complex web of veins, arteries and capillaries. Capillaries are tiny blood vessels that connect arteries and veins. People with HHT develop malformations in their capillaries. This means their capillaries aren’t linking their arteries and veins. Instead, they develop irregular links where capillaries normally are.

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When the capillary connection between your arteries and veins is abnormal, it’s called arteriovenous malformations (AVMs). People can have AVMs in almost any organ, such as in their nose, lungs, intestines or brain. A small AVM is called a telangiectasia. These appear as small, red lesions on your skin’s surface (sort of like a spider vein, but sometimes in the inner surface of your lips). AVMs typically refer to abnormalities in larger blood vessels, like those that affect your brain or lungs.

Both AVMs and telangiectasias can rupture or burst easily because they’re weak. This can cause chronic bleeding and other serious complications. Depending on the location of the rupture, it can be life-threatening.

The symptoms and severity of complications can vary. Many people go years without knowing they have HHT. While there’s no cure, there are many effective treatments for it.

The disorder is rare, but it’s also underdiagnosed, meaning many people have it without knowing. It affects 1 in 5,000 people worldwide, but a high percentage of people may never receive a diagnosis. HHT can affect anyone of any age and from all racial and ethnic groups. It’s inherited, so it runs in biological families.

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HHT is also called Osler-Weber-Rendu syndrome.

There are two types of HHT: HHT1 and HHT2. The difference between the two is which gene mutates or changes during fetal development. In HHT1, the ENG gene mutates. In HHT2 the ACVRL1 gene mutates. Other gene mutations can cause HHT, but researchers are still determining exactly how.

The symptoms of HHT vary from person to person, depending on where abnormal blood vessels develop in your body. Some people may have no significant signs, but others may develop very serious symptoms.

The most common symptom is frequent nosebleeds (epistaxis), which affect about 90% of people with HHT.

Some people with HHT have delicate red or purple spots on certain parts of their skin. They may get lighter when you press on them and are common on your:

• Face
• Fingers or fingertips
• Hands
• Lining of your mouth
• Lips
• Nose

Some people with HHT may also have the following symptoms due to bleeding:

• Anemia
• Black poop (bleeding in their stomach or intestines)

People with HHT may develop abnormalities in larger blood vessels — such as blood vessels in their spinal cord, lungs, brain and liver. This can cause:

• Blue discoloration of your skin
• Coughing up blood (hemoptysis)
• Fatigue
• Headaches
• Trouble breathing

Rare but serious complications can occur when an AVM ruptures, such as:

• Dizziness, double vision, seizures and strokes, if the condition affects blood vessels in your brain
• A brain abscess, which is a localized collection of pus within the brain tissue
• Back pain or numbness in your arms or legs, if HHT affects your spine

HHT is genetic, meaning it’s passed down from parents to children. It’s a dominant disorder, which means only one parent needs to have it for you to also have it. Hundreds of possible mutations in six different genes may cause HHT, but most cases are due to mutations in two genes, ENG and ACVRL1. Scientists are still studying the mutations and genes involved.

If you have HHT, there’s a 50% chance each child you have will inherit it.

The main risk factor is having a biological parent with the condition. If you have HHT, your children can get it, too. This doesn’t mean you shouldn’t have children, but you should be aware that your child has a 50% chance of having HHT if you have it.

Support from genetic counselors and other healthcare providers may be very helpful. If you believe you have HHT or a family history of HHT, ask your healthcare provider about genetic testing.

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HHT can cause potentially life-threatening bleeding and severe anemia. Complications from HHT vary widely, even within families.

Pulmonary AVMs (AVMs in your lungs) are the most common complication in people with HHT, occurring in about 40% of people. Common symptoms include shortness of breath, low oxygen levels and coughing up blood.

Other possible complications include:

• Heart failure
• High blood pressure in your lungs (pulmonary hypertension)
• Stroke

Early detection and treatment are best for preventing complications.

Genetic testing can identify HHT, but most people receive a diagnosis based on clinical information. A healthcare provider will likely:

• Ask questions about your medical history
• Ask questions about your parents’ medical history
• Examine your body for telangiectasia
• Order tests to take pictures of your organs

Your healthcare provider may diagnose HHT if they find at least three of the following:

• Repeat nosebleeds
• Multiple telangiectasias in the typical locations on your skin
• Internal telangiectasias or AVMs
• A family history of HHT

There are a few different tests your healthcare provider may order to confirm HHT. These include:

• Ultrasound: This test can determine if HHT is in your liver.
• Magnetic resonance imaging (MRI): MRI is especially helpful to check if HHT is affecting your brain.
• Bubble test: A bubble study is a special type of echocardiogram that checks for PAVM (HHT in your lungs).
• Computed tomography (CT) scan: A CT scan can show your organs in even more detail.

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You’re born with HHT. But many people don’t realize they have the condition until adulthood. The average age at which people show symptoms is 40 to 45 years old. You can receive a diagnosis at any time, though, even before birth.

There’s no cure for HHT, but treatments can improve symptoms and reduce the risk of serious complications. Scientists are still studying ways to treat HHT, including medicines that specifically target how blood vessels form.

Your healthcare provider treats you for existing symptoms and tests you for any HHT problems that haven’t shown symptoms yet.

Treatment may include:

• Ablation, a minor procedure to zap an area with a laser to make it stop bleeding
• Embolization, a procedure to block an area that’s bleeding or has a potential risk of bleeding
• Iron replacement or blood transfusion to treat anemia
• Lubrication and moisture for frequent nosebleeds
• Radiation to shrink or surgery to remove AVMs
• Avoiding certain over-the-counter medications that increase your risk of bleeding

You may need to see a specialist for treatment related to specific body systems, such as your liver, lungs, gastrointestinal system and brain.

If you have known or suspected pulmonary AVMs (PAVMs), you should take antibiotics before dental procedures to prevent infections, like brain abscesses.

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If you have HHT, you may need treatment for the rest of your life. You’ll also need regular checkups so your healthcare provider can monitor your overall health and treatment. There’s no cure, but treatment will ease your symptoms and reduce your risk of serious complications. If you have children, your provider may recommend they receive testing for the genetic mutations that cause HHT.

People with HHT have an almost average life expectancy when they receive the appropriate treatment.

There’s no way to prevent HHT or reduce your risk of getting it. But tell your healthcare provider if your parent, sibling or child has it. That can help you catch it early and prevent complications.

To help prevent nosebleeds:

• Avoid certain medications, such as aspirin and NSAIDs
• Keep a journal to track if any foods or activities trigger nosebleeds
• Keep your nose moist and lubricated all the time, using a humidifier, ointments and saline spray

If you’ve been diagnosed with HHT, consider asking your healthcare provider:

• Should anyone in my family get tested?
• Can I play sports?
• Should I avoid any particular activities?
• Should I avoid alcohol, certain foods or any medications?
• What can I do to prevent or stop nosebleeds?
• Is it safe for me to get pregnant?
• When should I seek medical attention for bleeding?

Yes, you can donate blood if you have HHT. Your healthcare provider may want to make sure your hematocrit levels are normal before you donate.

HHT is an inherited genetic disorder that often goes undiagnosed. Symptoms can range from frequent nosebleeds to serious complications like chronic bleeding. If you suspect that you or a family member has HHT, talk to your healthcare provider. Early treatment can prevent complications, and genetic testing can determine which family members have the condition.

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Cleveland Clinic’s health articles are based on evidence-backed information and review by medical professionals to ensure accuracy, reliability and up-to-date clinical standards.

Cleveland Clinic’s health articles are based on evidence-backed information and review by medical professionals to ensure accuracy, reliability and up-to-date clinical standards.

• Centers for Disease Control and Prevention (U.S.). Facts About Hereditary Hemorrhagic Telangiectasia (HHT). (https://www.cdc.gov/ncbddd/hht/index.html) Last reviewed 4/2023. Accessed 11/13/2025.
• Cure HHT (U.S.). What Is HHT? (https://curehht.org/understanding-hht/what-is-hht/) Accessed 11/13/2025.
• Merck Manual. Hereditary Hemorrhagic Telangiectasia (Osler-Weber-Rendu Syndrome). (https://www.merckmanuals.com/professional/hematology-and-oncology/bleeding-due-to-abnormal-blood-vessels/hereditary-hemorrhagic-telangiectasia) Last revised 5/2023. Accessed 11/13/2025.
• National Health Organization (U.K.). Hereditary haemorrhagic telangiectasia (HHT) (https://www.nhs.uk/conditions/hereditary-haemorrahagic-telangiectasia/). Last reviewed 5/2023. Accessed 11/13/2025.
• National Organization for Rare Disorders (U.S.). Hereditary Hemorrhagic Telangiectasia (https://rarediseases.org/rare-diseases/hereditary-hemorrhagic-telangiectasia/). Last updated 12/2021. Accessed 11/13/2025.

Do certain health conditions seem to run in your family? Are you ready to find out if you’re at risk? Cleveland Clinic’s genetics team can help.

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