Hereditary Hemorrhagic Telangiectasia (HHT)
Description
Hereditary Hemorrhagic Telangiectasia (HHT), also known as Osler-Weber-Rendu syndrome, is a genetic disorder that affects blood vessels. Individuals with HHT develop malformations of blood vessels, primarily in the skin, mucous membranes, lungs, brain, and liver. This can lead to recurrent nosebleeds, gastrointestinal bleeding, and even brain aneurysms. While there is no cure for HHT, there are effective treatments to manage symptoms and improve quality of life.
Genes Involved
Genes Involved in HHT:
- ENG (endoglin): Mutations in this gene are responsible for about 70% of HHT cases.
- ACVRL1 (ALK1): Mutations in this gene account for about 20% of HHT cases.
- SMAD4: Mutations in this gene are responsible for a rare form of HHT with a more severe presentation.
Recognizing the Signs and Symptoms
Recognizing the Signs and Symptoms of HHT:
- Recurrent Nosebleeds: This is the most common symptom, often starting in childhood. Nosebleeds may be frequent and severe, sometimes leading to anemia.
- Telangiectasias: These are small, dilated blood vessels that appear as red or purple marks on the skin, particularly on the face, lips, and fingertips.
- Gastrointestinal Bleeding: Bleeding from the stomach or intestines can occur due to malformations in the blood vessels of these organs.
- Pulmonary Arteriovenous Malformations (AVMs): These are abnormal connections between arteries and veins in the lungs, which can cause shortness of breath, fatigue, and even heart failure.
- Brain Aneurysms: In some cases, HHT can lead to the development of aneurysms (bulges) in blood vessels of the brain, which can rupture and cause a stroke.
- Liver Malformations: Blood vessel malformations in the liver can cause enlarged liver, pain, and complications such as portal hypertension.
Causes
Causes of Hereditary Hemorrhagic Telangiectasia (HHT):
HHT is caused by mutations in certain genes responsible for the normal formation and development of blood vessels. These genetic mutations are inherited from one or both parents. This means that if one parent has HHT, there is a 50% chance that their child will inherit the condition.
Inheritance/recurrence risk
Inheritance and Recurrence Risk:
HHT is an autosomal dominant disorder. This means that a person only needs to inherit one copy of the mutated gene from either parent to develop the condition. If one parent has HHT, there is a 50% chance of their child inheriting the disorder. If both parents have HHT, there is a 75% chance their child will inherit the condition.
