Hereditary haemorrhagic telangiectasia (HHT) is an inherited genetic disorder that affects the blood vessels. It's sometimes spelt hereditary hemorrhagic telangiectasia and is also known as Osler-Weber-Rendu syndrome.
Typical symptoms are persistent nosebleeds and visible red spots in certain places on the body – typically on the fingertip pads, on the lips and tongue, and on mucous membranes such as the lining of the nose and gut (see What are the symptoms?).
It affects about 1 in 5,000 people.
What happens in HHT?
In HHT, some of the blood vessels do not develop properly.
Normally, the arteries branch off into smaller and smaller blood vessels until they reach a network of capillaries (tiny blood vessels) that feed the body tissues and organs. Blood pressure drops in this network of capillaries, before the blood flows on into veins and back to the heart.
In HHT, some of the blood vessels from the arteries join directly with the veins. These abnormal connections are called arteriovenous malformations (AVMs).
When AVMs occur in small vessels near the surface of the skin, where they are visible as red spots, they are known as telangiectasia.
When they form in the lining of the nose or the gut, they can easily bleed. Frequent bleeding can lead to anaemia, and sometimes more serious problems (see What are the symptoms?).
What causes HHT?
Someone with HHT will have a faulty gene (genetic mutation) and, usually, this will have been inherited from one of their parents.
This gene normally provides instructions for making certain proteins found in the lining of the blood vessels. In HHT, the gene cannot produce this protein, or the protein it produces is abnormal.
You only need to have one copy of the faulty gene to develop HHT.
What are the symptoms?
Symptoms usually start in childhood or in the teenage years.
Often, the first sign is developing nosebleeds. They can start at any age, often in childhood. Nosebleeds may be frequent and persistent, but can improve with age.
They happen because of the abnormal blood vessels in the lining of the nose.
The loss of blood can lead to iron-deficiency anaemia, if the iron is not replaced through the diet and with iron supplements.
Red or purple spots under the skin (telangiectasia)
From about 20-30 years old (sometimes earlier), abnormal blood vessels – telangiectasia – may start to appear just underneath the skin, which show as red or purple spots.
Telangiectasia typically form on the fingertip pads, the lips, and the lining of the nose or the gut. Sometimes, they can form on the ears and face. They tend to increase in number with age.
They're usually just a cosmetic problem, although they may sometimes bleed.
Abnormal blood vessels (AVMs) inside the body
Arteriovenous malformations (AVMs) can form inside the body organs and tissues.
Many people with AVMs won't experience any symptoms, and are not even aware they have them. They can cause preventable complications, but most people live well with their AVMs.
Decisions to treat AVMs are based on the safety of the treatment versus the risks of leaving the AVM untreated. Some AVMs are worth treating, and some are better left alone.
AVMs in the lungs (pulmonary AVMs) often lead to low blood oxygen levels, and can allow blood clots to pass through to the brain, which could result in a stroke. They can occasionally bleed, but this is not very common outside of pregnancy. There are safe treatments available and these are usually recommended when pulmonary AVMs are found.
AVMs in the brain usually cause no symptoms, although they can irritate the surrounding brain tissue and cause seizures or headaches. They can also bleed, leading to a stroke, but whether they should be treated if they have not bled remains controversial.
AVMs in other parts of the body usually cause no symptoms.
How is HHT treated?
There's no cure for HHT, but there are effective treatments and life expectancy is usually very good.
Some patients can be managed by their GP, and some will need to be under the care of a specialist.
Because there are increased risks during pregnancy for women with HHT (such as a slight increased risk of a major bleed or a stroke), it is recommended that if HHT is in the family, this is brought to the attention of the specialist in charge of the woman's care.
Patients who have regular nosebleeds will probably lose a lot of iron through this loss of blood, especially if they also bleed from telangiectasia in the gut.
It is important to replace the lost iron with iron supplements – dietary changes alone may not be enough.
Read about the importance of iron and the treatment of anaemia with iron supplements and iron-rich food.
Treatment of nosebleeds
Those with severe nosebleeds may need emergency nasal packing, where the nose is packed with ribbon gauze or a special nasal sponge.
Some people may need to see an ear, nose and throat specialist for treatment. Laser therapy may help (see below).
More severe cases may respond to skin grafting or other surgery.
Blood transfusion after loss of blood
If a lot of blood has been lost from bleeding inside the body or after nosebleeds, a blood transfusion may be needed.
Read about blood transfusions.
Laser treatment for telangiectasia
Telangiectasia on the skin or in the lining of the nose can sometimes be improved with vascular laser or intense pulsed light (IPL) treatment.
For the skin, a referral to a dermatologist is usually needed. Around two to four treatments a year may be needed, so the overall cost may be significant if the treatment is not available on the NHS.
For the nose, a referral to an ear, nose and throat (ENT) specialist is needed, and these treatments are usually available on the NHS.
Laser and IPL machines produce narrow beams of light aimed at the visible blood vessels in the skin. The heat from the lasers damages the dilated veins and causes them to shrink so they are no longer visible, with minimal scarring or damage to the surrounding area.
Laser treatment can cause pain, but most people do not need an anaesthetic.
Treating AVMs inside the body
AVMs in the body may require specialist treatment. Your HHT specialist will explain any procedures to you in more detail.
For example, AVMs in the lung are usually treated, even if they are not causing any apparent problems. They are treated by embolisation, a procedure that blocks the blood supply to the AVM. A tiny plug is inserted inside the artery supplying the abnormal blood vessel.
Embolisation has virtually replaced open surgery, and is normally carried out under sedation (which will help relax you during the procedure).
For brain AVMs, embolisation, surgery and stereotactic radiotherapy (precisely delivering radiation to the blood vessel) are possible treatment options. Liver AVMs may require different types of specialist treatments.
However, these treatments aren't always appropriate. Your specialist will explain why many AVMs, such as those in the liver and in the brain, may be better left alone, as the risks of invasive treatments may outweigh the potential benefits.
Information about you
If you have HHT, your clinical team may pass information about you on to the National Congenital Anomaly and Rare Diseases Registration Service (NCARDRS).
This helps scientists look for better ways to prevent and treat this condition. You can opt out of the register at any time.
Find out more about the register.
Page last reviewed: 24/02/2015
Next review due: 24/02/2017