Hereditary hemorrhagic telangiectasia (HHT), also known as Osler-Weber-Rendu syndrome, is a genetic disorder of the blood vessels that can lead to abnormal blood vessel formation called arteriovenous malformation (AVM).

An abnormal blood vessel can become dilated, and cause severe bleeding, most commonly in the nose, lungs, brain and liver. Persistent bleeding can result in serious health problems if not promptly diagnosed and treated.

HHT affects about 1 in 5,000 people – 90% of whom are undiagnosed.

What causes HHT?

Hereditary hemorrhagic telangiectasia is passed down through families in an autosomal dominant pattern. This means the abnormal gene is needed from only one parent in order to inherit arteriovenous malformation or HHT.

The condition has been linked to multiple genes. Each gene is important for blood vessels to develop properly. HHT is caused by a mutation in any one of these genes.

Symptoms

People with HHT can develop AVMs in several areas of the body. If they are on the skin, including the lips, tongue or fingers, they are known as telangiectasia. The abnormal blood vessels can also develop in the brain, lungs, liver, intestines or in other areas.

A common symptom of HHT is frequent nosebleeds. Other symptoms include:

• Gastrointestinal bleeding, including loss of blood in the stool or dark stools
• Migraines, seizures or unexplained, small strokes
• Shortness of breath
• Enlarged liver
• Heart failure from vascular malformations
• Pulmonary hypertension
• Iron deficiency anemia

How is HHT diagnosed?

The health care provider will perform a physician examination and ask about your symptoms. A specialized provider can detect telangiectasia — or small, widened blood vessels on the skin — during a physical examination.

Tests include:

• Blood tests, including hemoglobin levels and iron panel
• Imaging test of the heart with agitated saline called a bubble echocardiogram
• CT scan of the lungs
• Endoscopy, which uses a tiny camera attached to a thin tube to look inside your body
• MRI or CT scan to detect AVMs in the brain
• CT or ultrasound scans to detect AVMs in the liver

There is often a family history of the condition. Genetic testing is available to look for changes in genes associated with this syndrome, such as internal cheek/buccal swab, saliva test or blood sample test. This can also help prospective parents understand the risks of passing the disease to their children.

A positive genetic test can confirm HHT. However, a negative genetic test result does not mean the disorder is not present.

Treatment

There is no cure for hereditary hemorrhagic telangiectasia, but treatments can improve symptoms and reduce the risk of serious complications. The most important aspect of HHT treatment is managing AVMs that cause dangerous bleeding. Treatment options include:

• Surgery to treat bleeding in some areas
• Sclerotherapy for nosebleeds
• Electrocautery (heating tissue with electricity), or laser surgery to treat frequent or heavy nosebleeds
• Endovascular embolization (injecting a substance through a thin tube) to treat abnormal blood vessels in the lungs, brain and other parts of the body

Iron may also be given if there is a lot of blood loss, leading to anemia. Avoid taking blood-thinning medication. Some drugs that affect blood vessel development are being studied as possible future treatments.

Therapies for bleeding may include:

• Saline nasal spray
• Mupirocin ointment
• Propranolol drops
• Doxycycline antibiotic
• Tranexamic acid or aminocaproic acid tablets
• Bevacizumab infusion
• Other antiangiogenic agents

A patient with pulmonary AVM may need to take antibiotics before having any dental work. They should avoid scuba diving to prevent decompression sickness (the bends). Ask your provider what other precautions you should take.

Support groups

Additional information and support for people with HHT disorder and their families can be found at:

• Cure HHT
• National Organization for Rare Disorders

Genetic counseling is recommended for couples who want to have children and who have a family history of HHT.

Outlook: what to expect

A patient with malformed blood vessels can live a completely normal lifespan with appropriate screening, depending on where in the body the AVMs are located.

Hereditary hemorrhagic telangiectasia is best treated by experienced health care professionals at a center that sees many patients with rare disorders. There are several HHT centers of excellence in the United States, including University of Florida Health, that offer optimal evaluation and care.