What is Hereditary Hemorrhagic Telangiectasia (HHT)? Symptoms, Causes, & Treatment

Hereditary Hemorrhagic Telangiectasia, or HHT, is a genetic condition that affects your blood vessels throughout your body. People with HHT have blood vessels that didn't form quite right during development, creating direct connections between arteries and veins without the usual tiny capillaries in between.

This condition used to be called Osler-Weber-Rendu syndrome, named after the doctors who first described it. While HHT is considered rare, affecting about 1 in 5,000 people worldwide, you might be surprised to learn that many people live with it without even knowing they have it.

What is HHT exactly?

HHT creates abnormal blood vessel connections called arteriovenous malformations, or AVMs for short. Think of your normal blood vessels like a well-organized highway system where blood flows from large arteries, through smaller streets called capillaries, and then into veins that carry blood back to your heart.

With HHT, some of these connections skip the capillary "streets" entirely, creating direct shortcuts between arteries and veins. These shortcuts can be tiny spots on your skin and mucous membranes, or they can be larger formations inside organs like your lungs, liver, or brain.

The smaller abnormal connections appear as small red or purple spots called telangiectasias. You'll typically see these on your lips, tongue, fingertips, and inside your nose. The larger connections, called AVMs, usually develop in internal organs and can vary significantly in size and impact.

What are the symptoms of HHT?

The most common and often first symptom you might notice is frequent nosebleeds, medically called epistaxis. These aren't your typical occasional nosebleeds but rather recurring ones that can happen multiple times per week or even daily.

Here are the main symptoms that people with HHT commonly experience:

• Frequent nosebleeds that may be heavy and difficult to stop
• Small red or purple spots on your lips, tongue, fingers, or face
• Shortness of breath during physical activity
• Fatigue that seems disproportionate to your activity level
• Iron deficiency anemia from ongoing blood loss

Some people may also experience symptoms related to AVMs in specific organs. If you have lung AVMs, you might feel short of breath or experience chest pain. Brain AVMs, while less common, can cause headaches, seizures, or even small strokes.

It's important to understand that HHT symptoms can vary dramatically between family members, even those with the same genetic type. Some people have mild symptoms that barely affect their daily life, while others may need more intensive medical management.

What are the types of HHT?

HHT comes in several genetic types, with the two most common being HHT1 and HHT2. Each type is caused by mutations in different genes, but they create similar overall symptoms with some notable differences.

HHT1, caused by mutations in the ENG gene, tends to cause more lung and brain AVMs. People with this type often experience more severe respiratory symptoms and have a higher likelihood of developing pulmonary AVMs that require monitoring and treatment.

HHT2, linked to mutations in the ACVRL1 gene, more commonly affects the liver and tends to cause liver AVMs. However, people with HHT2 can still develop lung AVMs, just less frequently than those with HHT1.

There are also rarer types, including HHT3 and HHT4, as well as some cases where the specific genetic cause hasn't been identified yet. These account for a smaller percentage of HHT cases but can have their own unique characteristics.

What causes HHT?

HHT is caused by mutations in genes that help control how blood vessels develop and maintain themselves. These genes normally act like instruction manuals for building healthy blood vessel connections, but when they're altered, the instructions get mixed up.

The condition follows what doctors call an autosomal dominant inheritance pattern. This means you only need to inherit one copy of the altered gene from one parent to develop HHT. If one of your parents has HHT, you have a 50% chance of inheriting it.

Sometimes, HHT can occur as a new mutation, meaning neither parent has the condition but a genetic change happened during early development. These spontaneous cases are less common but do occur, accounting for about 20% of HHT cases.

The genes most commonly involved include ENG, ACVRL1, and SMAD4. These genes normally help cells communicate properly during blood vessel formation, ensuring that arteries, capillaries, and veins connect in the right way.

When should you see a doctor for HHT?

You should consider seeing a doctor if you're experiencing frequent nosebleeds, especially if they're becoming more severe or happening multiple times per week. While occasional nosebleeds are normal, persistent ones that interfere with your daily life warrant medical attention.

Seek medical care if you notice small red or purple spots developing on your lips, tongue, or fingertips, particularly if you also have a family history of similar symptoms. These telangiectasias, combined with recurrent nosebleeds, are classic early signs of HHT.

You should seek immediate medical attention if you experience sudden shortness of breath, chest pain, severe headaches, or any neurological symptoms like vision changes or weakness. These could indicate complications from AVMs in your lungs or brain that need urgent evaluation.

If you have a family history of HHT, it's worth discussing genetic counseling and screening with your healthcare provider, even if you don't have obvious symptoms. Early detection can help prevent complications through proper monitoring and preventive care.

What are the risk factors for HHT?

The primary risk factor for HHT is having a family history of the condition. Since HHT follows an autosomal dominant inheritance pattern, having one affected parent gives you a 50% chance of inheriting the condition.

Your risk increases significantly if multiple family members have experienced frequent nosebleeds, unexplained anemia, or have been diagnosed with lung, liver, or brain AVMs. Sometimes, family members may have had symptoms but never received a proper diagnosis.

Age can influence when symptoms become apparent. While HHT is present from birth, symptoms often worsen over time. Nosebleeds might start in childhood, while organ AVMs may not cause symptoms until adulthood.

Pregnancy can sometimes worsen HHT symptoms due to increased blood volume and hormonal changes. Women with HHT may experience more frequent or severe nosebleeds during pregnancy and may need closer monitoring.

What are the possible complications of HHT?

While many people with HHT live relatively normal lives, the condition can lead to several complications that require ongoing medical attention. Understanding these possibilities can help you work with your healthcare team to prevent or manage them effectively.

The most common complications include:

• Iron deficiency anemia from chronic blood loss through nosebleeds
• Pulmonary AVMs that can cause shortness of breath or, rarely, stroke
• Liver AVMs that may affect liver function over time
• Brain AVMs that can cause headaches, seizures, or neurological symptoms
• High-output heart failure from liver AVMs in severe cases

Pulmonary AVMs deserve special attention because they can allow blood clots or bacteria to bypass the lungs' natural filtering system. This creates a small risk of stroke or brain abscess, which is why people with lung AVMs often receive preventive antibiotics before dental procedures.

In rare cases, large liver AVMs can cause the heart to work harder, potentially leading to heart failure over many years. Brain AVMs, while less common, can occasionally rupture and cause bleeding in the brain, though this is relatively uncommon.

How can HHT be prevented?

Since HHT is a genetic condition, you can't prevent it from occurring if you inherit the altered genes. However, you can take steps to prevent complications and manage symptoms effectively once you know you have the condition.

If you're planning to have children and have HHT or a family history of it, genetic counseling can help you understand the risks and options. Prenatal genetic testing is available if you want to know whether your baby will inherit the condition.

For managing existing HHT, prevention focuses on avoiding activities that might trigger severe nosebleeds and maintaining good overall health. This includes using a humidifier, avoiding nose picking, and being gentle when blowing your nose.

Regular medical monitoring is crucial for preventing serious complications. This typically includes periodic imaging studies to check for new AVMs and monitoring iron levels to prevent severe anemia.

How is HHT diagnosed?

Doctors diagnose HHT using a combination of clinical criteria and genetic testing. The diagnosis often starts with recognizing a pattern of symptoms, particularly the combination of recurrent nosebleeds and characteristic telangiectasias.

The Curacao Criteria are used to diagnose HHT based on four main features: spontaneous recurrent nosebleeds, telangiectasias in characteristic locations, visceral AVMs, and a family history of HHT. Having three or more criteria makes the diagnosis definitive.

Genetic testing can confirm the diagnosis and identify the specific type of HHT you have. This information helps doctors understand which complications you might be more likely to develop and plan appropriate screening schedules.

Your doctor may also order imaging studies like CT scans or MRI to look for AVMs in your lungs, liver, or brain. An echocardiogram with bubble study is commonly used to screen for lung AVMs, as it's a safe and effective initial test.

What is the treatment for HHT?

Treatment for HHT focuses on managing symptoms and preventing complications rather than curing the underlying condition. Your treatment plan will be tailored to your specific symptoms and the locations of any AVMs you may have.

For nosebleeds, treatments range from simple moisturizing measures to more advanced procedures. Options include nasal saline rinses, humidification, topical treatments, laser therapy, or even nasal closure procedures in severe cases.

Here are the main treatment approaches:

• Iron supplementation and blood transfusions for anemia
• Embolization procedures to block problematic AVMs
• Surgical removal of accessible AVMs when appropriate
• Medications to reduce bleeding tendencies
• Preventive antibiotics before dental or surgical procedures

Large lung AVMs are typically treated with embolization, a procedure where tiny coils or plugs are placed to block the abnormal connection. This is usually done as an outpatient procedure and can significantly reduce the risk of stroke or other complications.

Liver AVMs are often monitored rather than treated unless they're causing heart problems. Brain AVMs require careful evaluation by neurosurgical specialists to determine if treatment is necessary and safe.

How can you manage HHT at home?

Living well with HHT involves developing daily habits that minimize symptoms and reduce your risk of complications. Most people find that simple lifestyle adjustments can make a significant difference in their quality of life.

For nosebleed management, keep your nasal passages moist using saline sprays or a humidifier, especially during dry weather. Apply a thin layer of petroleum jelly or nasal gel to the inside of your nostrils before bed to prevent drying and cracking.

When a nosebleed occurs, lean forward slightly and pinch the soft part of your nose for 10-15 minutes. Avoid tilting your head back, as this can cause blood to run down your throat and potentially cause nausea.

Monitor your energy levels and watch for signs of anemia like unusual fatigue, shortness of breath, or pale skin. Keep track of your nosebleed frequency and severity to discuss with your healthcare team during visits.

Stay up to date with preventive care, including dental cleanings and any recommended imaging studies. If you have lung AVMs, remember to take prescribed antibiotics before dental procedures to prevent potential infections.

How should you prepare for your doctor appointment?

Preparing for your HHT-related medical appointments can help ensure you get the most comprehensive care possible. Start by keeping a symptom diary that tracks your nosebleeds, including their frequency, duration, and severity.

Gather your family medical history, particularly noting any relatives who have had frequent nosebleeds, unexplained anemia, lung problems, or strokes at a young age. This information can be crucial for both diagnosis and genetic counseling.

Bring a list of all your current medications, including over-the-counter supplements and vitamins. Some medications can affect bleeding tendencies, so your doctor needs a complete picture of what you're taking.

Write down any questions you have about your condition, treatment options, or lifestyle modifications. Don't hesitate to ask about genetic counseling if you're planning to have children or if other family members might be affected.

What's the key takeaway about HHT?

HHT is a manageable genetic condition that affects blood vessel formation throughout your body. While it can cause troublesome symptoms like frequent nosebleeds and requires ongoing medical monitoring, most people with HHT live full, active lives with proper care.

The key to living well with HHT is early diagnosis, regular monitoring for complications, and working closely with a healthcare team familiar with the condition. Many symptoms can be effectively managed with appropriate treatments and lifestyle modifications.

If you suspect you might have HHT based on symptoms or family history, don't hesitate to discuss it with your healthcare provider. Early detection and proper management can prevent serious complications and significantly improve your quality of life.

Remember that having HHT doesn't define your life's limitations. With proper medical care and self-management strategies, you can pursue your goals and maintain excellent overall health while managing this condition.