What is Hereditary Hemorrhagic Telangiectasia (HHT), also known as Osler-Weber-Rendu syndrome?

From the Guidelines

Hereditary Hemorrhagic Telangiectasia (HHT), also known as Osler-Weber-Rendu syndrome, is a genetic disorder characterized by abnormal blood vessel formation, leading to telangiectasias and arteriovenous malformations (AVMs) in various organs, with a prevalence of approximately 1 in 5000, as stated in the second international guidelines for the diagnosis and management of HHT 1.

Key Characteristics of HHT

• Autosomal dominant inheritance pattern, with mutations in genes such as ENG, ACVRL1, or SMAD4, affecting blood vessel formation 1
• Telangiectasias on the skin and mucous membranes, and AVMs in larger organs like the lungs, liver, and brain
• Primary symptoms include recurrent nosebleeds, gastrointestinal bleeding, and iron deficiency anemia

Diagnosis and Management

• Diagnosis is based on the Curaçao criteria, which include epistaxis, telangiectasias, visceral AVMs, and family history 1
• Management focuses on controlling bleeding episodes and preventing complications from AVMs, with treatments such as:

• Moisturizing the nasal passages with saline sprays or petroleum jelly for nosebleeds
• Tranexamic acid (1-1.5g orally three times daily during severe episodes) or procedures like laser therapy or septodermoplasty for severe cases
• Iron supplementation (typically ferrous sulfate 325mg daily) or intravenous iron for anemia

• Screening for organ AVMs, including brain MRI, contrast echocardiography, and abdominal imaging, is essential to prevent complications 1

Complications and Prevention

• Pulmonary AVMs require embolization to prevent stroke or brain abscess
• Liver AVMs may need management of high-output heart failure with medications like beta-blockers
• Brain AVMs often require neurosurgical intervention The second international guidelines for the diagnosis and management of HHT provide evidence-based consensus guidelines for the management and prevention of HHT-related symptoms and complications, emphasizing the importance of early diagnosis and screening to improve outcomes 1.

From the Research

Definition and Characteristics of Hereditary Hemorrhagic Telangiectasia (HHT)

• Hereditary Hemorrhagic Telangiectasia (HHT), also known as Osler-Weber-Rendu syndrome, is a rare autosomal dominant genetic disorder that leads to abnormal blood vessel formation in the skin, mucus membranes, and organs such as the lung, liver, and brain 2, 3, 4, 5, 6.
• The disorder occurs due to a mutation in one of the ACVRL1, ENG, and SMAD4 genes, which code for the formation of blood vessels 2, 3, 4.
• HHT is characterized by the presence of telangiectasias and arteriovenous malformations (AVMs) in various organs, leading to complications such as bleeding, anemia, iron deficiency, and high-output heart failure 3, 6.

Clinical Features and Symptoms of HHT

• The most common symptom of HHT is recurring nosebleed (epistaxis), which begins in childhood and affects about 90-95% of people with HHT 2.
• Other common signs and symptoms include punctate, linear, or splinter-like telangiectasias on the upper body, oral mucosa, or nail beds, gastrointestinal bleeding, and iron deficiency anemia 2, 6.
• Patients with HHT may also experience telangiectases of the oral buccal mucosa, tongue and/or lips, pulmonary AVMs, hepatic AVMs, gastrointestinal telangiectases, and encephalic AVMs 6.

Diagnosis and Management of HHT

• The diagnosis of HHT is clinical, based on the Curaçao criteria, and involves clinical screening, baseline investigations, genetic testing, and detailed medical imaging to detect visceral AVMs 2, 3.
• Management of HHT includes intravenous iron therapy or blood transfusion, antifibrinolytics, ablation therapies, and systemic anti-angiogenic agents such as bevacizumab and thalidomide 2, 3, 4, 6.
• A multidisciplinary approach is necessary for the early diagnosis and optimal management of patients with HHT, and otolaryngologists play a critical role in the identification and management of HHT 5, 6.