Hereditary hemorrhagic telangiectasia

What is Hereditary hemorrhagic telangiectasia?

Hereditary hemorrhagic telangiectasia (HHT), also known as Osler-Weber-Rendu syndrome, is a rare genetic disorder that affects blood vessel formation throughout the body. The condition causes abnormal connections between arteries and veins, leading to fragile blood vessels that bleed easily and arteriovenous malformations (AVMs) in various organs. HHT affects approximately 1 in 5,000 to 8,000 people worldwide, making it more common than many other rare diseases. While symptoms can appear at any age, they typically become more apparent during adulthood, with many patients experiencing a long diagnostic journey before receiving proper care.

Key statistics

Symptoms

The primary symptoms include recurrent nosebleeds, gastrointestinal bleeding, small red spots on skin and mucous membranes, and arteriovenous malformations in lungs, brain, or liver.

Early and common symptoms:
Recurrent epistaxis (nosebleeds) is often the first and most common symptom, affecting over 90% of patients. These nosebleeds typically begin in childhood or adolescence and may be severe or frequent enough to cause anemia. Small, red spider-like blood vessel clusters called telangiectasias appear on the lips, tongue, fingertips, and inside the nose and mouth. These lesions are painless but may bleed when touched.

Progressive symptoms:
Gastrointestinal bleeding may develop, often presenting as iron-deficiency anemia, black stools, or blood in vomit. Shortness of breath, particularly during exercise, may indicate pulmonary AVMs. Some patients experience fatigue related to chronic blood loss and anemia.

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Serious complications:
Large arteriovenous malformations can develop in the lungs, brain, liver, or spinal cord. Pulmonary AVMs may cause stroke or brain abscess due to blood clots or bacteria bypassing the lungs’ filtering system. Cerebral AVMs can lead to seizures, headaches, or hemorrhagic stroke. Hepatic AVMs may cause heart failure or liver dysfunction in severe cases.

Causes and risk factors

HHT is caused by mutations in genes that control blood vessel development. The most common mutations occur in the ENG gene (causing HHT1) and the ACVRL1 gene (causing HHT2), which together account for approximately 85% of cases. Less commonly, mutations in SMAD4 and GDF2 genes can cause HHT. These genes normally help regulate the formation of blood vessels and ensure proper connections between arteries and veins.

The condition follows an autosomal dominant inheritance pattern, meaning only one copy of the mutated gene is needed to cause the disease. Each child of an affected parent has a 50% chance of inheriting the condition. However, approximately 20% of cases result from new mutations with no family history.

The primary risk factor is having an affected parent or family member. The severity and specific symptoms can vary significantly, even within the same family, due to the variable expression of the genetic mutations.

Prevention

Since HHT is a genetic condition, it cannot be prevented. However, genetic counseling and testing can help families understand their risks and make informed reproductive decisions. Preimplantation genetic testing may be available for couples with known HHT mutations who wish to avoid passing the condition to their children.

For individuals with HHT, preventive screening can help identify and treat complications before they become life-threatening. Regular screening for pulmonary and cerebral AVMs is recommended, even in asymptomatic patients. Preventive measures also include avoiding activities that increase bleeding risk and maintaining good oral hygiene to prevent dental infections that could lead to brain abscesses in patients with pulmonary AVMs.

Complications

Without proper management, HHT can lead to serious, life-threatening complications. Untreated pulmonary AVMs pose risks for paradoxical stroke, brain abscess, and massive hemoptysis. The risk of stroke from pulmonary AVMs is particularly concerning, as blood clots can bypass the lungs’ natural filtering system and travel directly to the brain.

Cerebral AVMs can rupture, causing hemorrhagic stroke, seizures, or focal neurological deficits. Chronic bleeding from telangiectasias and gastrointestinal lesions often leads to iron-deficiency anemia, requiring ongoing iron supplementation or blood transfusions. Severe hepatic AVMs can result in high-output heart failure, portal hypertension, or hepatic encephalopathy.

The psychological impact of living with a chronic bleeding disorder can also be significant, affecting quality of life and social functioning.

Diagnosis

Diagnosis relies primarily on clinical criteria known as the Curaçao criteria, which include: spontaneous recurrent epistaxis, multiple telangiectasias at characteristic sites (lips, oral cavity, fingers, nose), visceral lesions (pulmonary, hepatic, cerebral, or spinal AVMs), and a first-degree relative with HHT. A definite diagnosis requires three or more criteria, while two criteria suggest possible HHT.

Imaging studies play a crucial role in identifying AVMs. Contrast echocardiography with saline bubble study screens for pulmonary AVMs, while chest computed tomography (CT) provides detailed visualization. Magnetic resonance imaging (MRI) or CT angiography evaluates cerebral and spinal AVMs. Gastrointestinal endoscopy may be necessary to identify bleeding sources in the digestive tract.

Genetic testing can confirm the diagnosis and identify the specific mutation, which is valuable for family screening and genetic counseling. Testing typically examines the ENG, ACVRL1, SMAD4, and GDF2 genes. However, genetic testing may not identify mutations in all patients, as additional genes may be involved.

Treatment

Treatment for HHT is primarily supportive and focuses on managing symptoms and preventing complications. There is currently no cure for the underlying condition.

For epistaxis management, topical treatments include nasal moisturizers, tranexamic acid, and estrogen-containing preparations. Laser therapy, electrocautery, or nasal packing may be necessary for severe bleeding. Some patients benefit from bevacizumab, an anti-angiogenic medication that can reduce bleeding in severe cases.

Iron supplementation is essential for managing anemia, often requiring oral ferrous sulfate or intravenous iron preparations. Severe anemia may necessitate blood transfusions.

Pulmonary AVMs larger than 3mm typically require treatment with transcatheter embolization to prevent stroke and brain abscess. Cerebral AVMs may be treated with surgical resection, stereotactic radiosurgery, or endovascular embolization, depending on their size and location.

Tranexamic acid can help control acute bleeding episodes. Some patients benefit from aminocaproic acid for bleeding control.

Prognosis

The prognosis for HHT varies significantly depending on the severity of AVMs and how early they are detected and treated. With appropriate screening and management, many patients live normal lifespans with good quality of life. Early identification and treatment of pulmonary and cerebral AVMs dramatically improve outcomes and prevent life-threatening complications.

Patients with severe hepatic involvement or multiple large AVMs may have a more guarded prognosis. The condition is progressive, with symptoms typically worsening with age, particularly epistaxis and the development of new telangiectasias. Regular monitoring and preventive treatment of AVMs are essential for maintaining good long-term outcomes.

Life expectancy can be near normal with proper medical care, though quality of life may be affected by chronic bleeding and the need for ongoing medical interventions.

Quality of life

Living with HHT requires ongoing vigilance and lifestyle modifications to minimize bleeding risks and manage symptoms. Many patients develop effective coping strategies for managing frequent nosebleeds, including carrying tissue, avoiding nasal trauma, and using humidifiers to prevent nasal dryness.

Regular exercise is generally beneficial, though contact sports and activities with high injury risk should be avoided. Swimming and other low-impact activities are usually well-tolerated. Adequate nutrition, particularly iron-rich foods, helps combat anemia, though dietary measures alone are rarely sufficient.

Sleep quality may be affected by nasal congestion and bleeding. Using a humidifier and sleeping with the head elevated can help reduce nighttime nosebleeds. Stress management is important, as stress can worsen bleeding symptoms in some patients.

Many patients find support groups and online communities helpful for sharing practical tips and emotional support. Maintaining open communication with healthcare providers and family members about symptoms and concerns is crucial for optimal management.

Pregnancy and fertility

HHT generally does not affect fertility, but pregnancy requires special consideration due to increased bleeding risks and cardiovascular changes. The increased blood volume during pregnancy can worsen epistaxis and may affect hepatic AVMs. Pulmonary AVMs may also pose increased risks during pregnancy due to hormonal changes and increased cardiac output.

Pre-pregnancy counseling should include screening for pulmonary and cerebral AVMs, as these may require treatment before conception. Some medications used to manage HHT symptoms may need adjustment during pregnancy. Genetic counseling is important to discuss the 50% risk of transmitting HHT to offspring.

Delivery planning should involve a multidisciplinary team, particularly for women with significant pulmonary or hepatic AVMs. Most women with HHT can have successful pregnancies with appropriate monitoring and care.

Children

Children with HHT may present with recurrent nosebleeds as the earliest symptom, though telangiectasias and AVMs typically develop later. Screening for pulmonary AVMs is generally recommended by age 5-10 years, even in asymptomatic children, as these lesions can be present without obvious symptoms.

Parents should be educated about recognizing signs of complications, such as persistent headaches, seizures, or shortness of breath. Schools should be informed about the child’s condition to ensure appropriate response to nosebleeds and to avoid activities that might increase bleeding risk.

Regular follow-up with pediatric specialists familiar with HHT is important for monitoring development of new AVMs and managing symptoms as they arise.

When to see a doctor

Urgent medical attention is needed for sudden severe headache, neurological symptoms (weakness, speech changes, seizures), persistent chest pain, significant shortness of breath, coughing up blood, or signs of severe bleeding such as dizziness, rapid heart rate, or pallor.

Routine follow-up is important for worsening nosebleeds, new skin lesions, symptoms of anemia (fatigue, weakness), or any new concerning symptoms. Regular screening appointments should be maintained even when feeling well, as AVMs can develop or enlarge without symptoms.

Annual or bi-annual check-ups with an HHT specialist are recommended for optimal management and screening.

Regional context

Limited data exists on HHT prevalence specifically in the Caucasus region (Georgia, Armenia, Azerbaijan) and Eastern Mediterranean. The condition likely occurs at similar rates as in other populations, though certain founder mutations may be more common in specific ethnic groups. Regional medical centers are increasingly recognizing HHT, though diagnostic delays may still occur due to limited awareness.

We invite healthcare professionals and researchers from these regions to contribute their experiences and data to improve understanding of HHT’s regional characteristics and optimize local care pathways.

Research and clinical trials

Current research focuses on developing new treatments to reduce bleeding and prevent AVM growth. Anti-angiogenic therapies, including bevacizumab and other VEGF inhibitors, show promise for reducing bleeding symptoms. Gene therapy approaches are being investigated for potential future treatments.

Clinical trials are exploring novel approaches including topical medications for epistaxis, new embolization techniques for AVMs, and drugs to promote normal blood vessel development. The organization Cure HHT actively supports research initiatives and maintains databases of ongoing studies.

Patients interested in clinical trials can search ClinicalTrials.gov for current opportunities or contact Cure HHT for information about research participation.

Frequently asked questions

Will my children definitely inherit HHT if I have it?

No, each child has a 50% chance of inheriting HHT due to its autosomal dominant pattern. Genetic testing and counseling can help families understand their specific risks and options.

Can HHT be cured?

Currently, there is no cure for HHT, but treatments can effectively manage symptoms and prevent complications. Research is ongoing for potential future therapies that might address the underlying cause.

How often do I need screening for AVMs?

Screening frequency depends on your specific situation and previous results. Generally, initial screening for pulmonary and cerebral AVMs is recommended, with follow-up intervals determined by your HHT specialist based on findings and symptoms.

Is it safe to take blood thinners if I have HHT?

Blood thinners require careful consideration in HHT patients due to increased bleeding risks. The decision depends on your specific medical needs and bleeding severity, and should always be made in consultation with your healthcare team.

Can dietary changes help with HHT symptoms?

While diet cannot cure HHT, iron-rich foods can help combat anemia, and staying well-hydrated may help reduce nosebleeds. However, dietary measures alone are rarely sufficient, and medical treatment is typically necessary.

Support and resources

International organizations:
– Cure HHT (curehht.org) – Primary patient advocacy organization with comprehensive resources
– Orphanet (orpha.net) – European database of rare diseases and orphan drugs
– National Organization for Rare Disorders (NORD) (rarediseases.org)
– EURORDIS (eurordis.org) – European rare disease alliance
– World Health Organization (WHO) rare disease resources (who.int)

Regional support:
– HHT support groups exist in many countries and can be found through Cure HHT
– Online communities provide peer support and practical advice for daily management

Related conditions

Pulmonary arteriovenous malformations
Cerebral arteriovenous malformations
Iron deficiency anemia
Epistaxis
Gastrointestinal bleeding

Sources: Orphanet (orpha.net), OMIM, GeneReviews (NCBI), WHO ICD-11, relevant guidelines. Informational only; not medical advice. CC BY 4.0.

Licensed under CC BY 4.0. Free to share with attribution to GMJ News.

Sources: Orphanet (orpha.net), OMIM, GeneReviews (NCBI), WHO ICD-11, EULAR/ACR guidelines. Schema.org MedicalCondition structured data included.