HHT

Hereditary Hemorrhagic Telangiectasia (HHT), also known as Osler-Weber-Rendu disease, is a genetic disorder that affects the development of blood vessels, leading to abnormal blood vessel formation. These abnormalities can cause bleeding, known as telangiectasias, in the skin, mucous membranes, and sometimes in organs such as the liver, brain, and lungs. HHT is an autosomal dominant condition, meaning that a mutation in just one of the two copies of the gene a person has is sufficient to cause the disorder.

Symptoms and Signs

The symptoms of HHT can vary widely among affected individuals, even within the same family. Common signs include:

• Nosebleeds (Epistaxis): The most common symptom, often starting in childhood.
• Skin Telangiectasias: Small, red or purple spots on the skin, particularly on the lips, nose, fingers, and ears.
• Organ AVMs: Arteriovenous malformations (AVMs) in organs such as the brain, lungs, and liver can lead to serious complications if untreated.

Genetics

HHT is caused by mutations in several genes, with the most common being ENG, ACVRL1 (also known as ALK1), and SMAD4. These genes are involved in the development and maintenance of blood vessel walls. The inheritance pattern is autosomal dominant, meaning that having a mutation in just one copy of the gene is enough to cause the disorder.

Diagnosis

Diagnosis of HHT is based on the Curacao Criteria, which includes:

1. Spontaneous and recurrent nosebleeds.
2. Multiple telangiectasias in typical locations.
3. Proven visceral AVMs (e.g., in the lungs, liver, brain, or spine).
4. A first-degree relative with HHT.

A diagnosis of HHT is considered definite if three of the criteria are met, possible or suspected if two criteria are met, and unlikely if fewer than two are met.

Treatment

There is no cure for HHT, but treatments are available to manage symptoms and reduce the risk of complications. Treatment options may include:

• Laser therapy for skin and mucous membrane telangiectasias.
• Embolization or surgery for AVMs in critical organs.
• Iron supplements and blood transfusions for anemia due to frequent nosebleeds.

Prognosis

The prognosis for individuals with HHT varies depending on the organs affected and the severity of the AVMs. With appropriate management, most people with HHT live normal lifespans, although they may require ongoing treatment for bleeding and other complications.

See Also

• Genetic disorder
• Blood vessel
• Arteriovenous malformation