Hereditary Hemorrhagic Telangiectasia (HHT)
What is hereditary hemorrhagic telangiectasia (HHT)?
Hereditary hemorrhagic telangiectasia (HHT), also known as Osler-Weber-Rendu syndrome, is a genetic disorder that affects how blood vessels are formed. The blood vessels that form incorrectly are called telangiectases. These spots are prone to breaking open and bleeding. People with HHT often have nosebleeds (epistaxis) when younger. About 25% of these people later develop gastrointestinal bleeding.
Telangiectases that form in large blood vessels are called arteriovenous malformations (AVMs). AVMs lack capillaries and directly connect veins and arteries. These malformations can be very dangerous when found in the lungs (pulmonary AVMs or PAVMs), the liver, or in the brain.
Who gets hereditary hemorrhagic telangiectasia (HHT)?
HHT is a genetic disease. It is a “dominant” disorder, meaning that it is caused by one copy of one abnormal gene from one parent. If one parent has HHT there is 50% chance the child will get HHT. If your parents have HHT but you don’t, you cannot pass the gene onto your children or grandchildren.
How common is hereditary hemorrhagic telangiectasia (HHT)?
The incidence of HHT is hard to tell since there are such a wide variety of symptoms. It is known that HHT occurs in many ethnic groups. While many people go undiagnosed, there are currently about 500,000 people diagnosed with it around the world.
Symptoms and Causes
What causes hereditary hemorrhagic telangiectasia (HTT)?
HTT is caused by an abnormal gene on chromosome 9 or 12 is the cause of HHT. Individuals with this abnormal gene are not able to make the bodily substance that forms blood vessels.
What are the common signs and symptoms of hereditary hemorrhagic telangiectasia (HHT)?
Some commons signs of HHT include:
- Reoccurring and frequent nosebleeds
- Telangiectases that appear on the skins surface in your 30s and 40s
- Black stools and anemia
- Back pain and loss of feeling in the arms and legs
Telangiectases and arteriovenous malformations (AVMs) typically form:
- In the nose
- The lining of the stomach and intestines
- On the skin of the face, hands, and mouth
Diagnosis and Tests
How is hereditary hemorrhagic telangiectasia (HHT) diagnosed?
A patient is clinically diagnosed if three or more of these symptoms are present:
- Nosebleed—Spontaneous and frequent nosebleeds
- Telangiectases cause red blotches on the lips, oral cavity, fingers, and nose
- Arteriovenous malformations (AVMs) are present in the lungs, brain, stomach, intestines, liver, or spine
- There is a first-degree relative that has been diagnosed with HHT
Is there a test for hereditary hemorrhagic telangiectasia (HHT)?
Yes. Genetic testing can be done if there is clinical evidence that an immediate family member has HHT. Genetic testing for HHT is expensive and complex. It will be done on multiple members in the immediate family if one member has been diagnosed. There are only a few laboratories that test for HHT in the United States. If three or more of the above symptoms are present, genetic testing is not always necessary to be properly diagnosed.
Management and Treatment
Can hereditary hemorrhagic telangiectasia (HHT) be treated?
Yes. Although telangiectases and arteriovenous malformations (AVMs) aren’t preventable, most cases are treatable when they start to appear. They should be treated if they are causing or can cause a serious problem. The recommended treatment for telangiectases and AVMs depend on the size and location of them on the body. The following treatments are recommended for each symptom:
- Nose bleeds—At-home humidifiers, over-the-counter ointments, laser coagulation therapy, septal dermoplasty (replacing the mucous membranes with a thick layer of skin), and embolization (blocking off an artery)
- Bleeding from the stomach and intestines (only treated if it causes anemia)—Iron therapy, a transfusion, endoscopic treatments, and hormonal treatments
- Lung AVMs—Embolization (blocking off the artery leading to the AVM to stop blood flow)
- Brain AVMs—Surgery, embolization, and stereotactic radiosurgery can be done separately or in conjunction with each other depending on the size and location of the AVM in the brain.
- Liver AVMs—Liver AVMs are only treated if the patient shows signs of liver or heart failure. Embolization can cause severe complications when done on the liver.