Medicine
Hereditary Hemorrhagic Telangiectasia: Diagnosis and Multidisciplinary Management
Quick fact
Hereditary hemorrhagic telangiectasia (HHT) affects about 1 in 5,000 to 10,000 people worldwide, yet many remain undiagnosed until they develop a serious complication like a stroke from a pulmonary arteriovenous malformation.
Why this is interesting
You might know someone who gets frequent nosebleeds, but what if those nosebleeds are a clue to a hidden network of abnormal blood vessels? Hereditary hemorrhagic telangiectasia (HHT) turns out to be a common cause of mysterious nosebleeds and can even lead to serious complications like strokes.
Read the full explanation
Understanding Hereditary Hemorrhagic Telangiectasia: Diagnosis and Multidisciplinary Management
Imagine your blood vessels as a network of pipes. In HHT, a genetic mutation weakens the structure of small vessels, causing them to stretch and form direct connections between arteries and veins without the normal capillary bed in between. These abnormal connections, called arteriovenous malformations (AVMs), are fragile and can rupture, causing bleeding. The most common sign is spontaneous, recurrent nosebleeds, which often begin in childhood. Over time, tiny red spots called telangiectasias appear on the lips, tongue, fingers, and inside the nose. Diagnosis begins with the Curacao criteria: spontaneous recurrent nosebleeds, telangiectasias in characteristic spots, visceral AVMs (in lungs, liver, or brain), and a first-degree relative with HHT. If at least three criteria are present, a clinical diagnosis is made; genetic testing confirms it. Because HHT can affect many organs, management requires a coordinated team of specialists: an ENT for nosebleeds, a pulmonologist for lung AVMs, a gastroenterologist for bleeding in the gut, a hepatologist for liver issues, and a neurologist for brain AVMs. Treatment ranges from iron supplements and nasal care to embolization of AVMs, and in severe cases, surgery.
A deeper explanation
The root cause of HHT lies in mutations of genes like ENG, ACVRL1, and SMAD4, which are part of the TGF-beta signaling pathway essential for maintaining the integrity and normal development of blood vessels. When this pathway is disrupted, the structure of the vessel wall becomes compromised, particularly in venules, leading to their dilation and direct shunting with arterioles. This explains why AVMs and telangiectasias form. The diagnosis is not only clinical but increasingly relies on genetic testing, which also helps identify family members at risk. Management is unapologetically multidisciplinary because each organ system can be affected differently; for instance, pulmonary AVMs pose a risk for paradoxical embolism leading to stroke or brain abscess, so screening with contrast echocardiography is recommended. Brain AVMs can cause severe bleeding, and liver involvement can cause heart failure. Therefore, coordinated care is crucial: after diagnosis, patients undergo systematic screening for visceral AVMs, and each AVM is managed according to its location and risk. Treatments include anti-angiogenic agents like bevacizumab, which reduce nosebleeds and anemia, and interventional procedures like embolization. Understanding the mechanism helps clinicians anticipate complications and customize management, emphasizing that a rare disease like HHT is best managed by a team rather than a single specialist.