What is hereditary haemorrhagic telangiectasia?
Hereditary haemorrhagic telangiectasia (HHT) is a condition where malformations of small blood vessels occur in multiple areas throughout the body. These so-called arteriovenous malformations (AVMs) commonly occur in the nose, causing nosebleeds, which occasionally can be severe.
Hereditary haemorrhagic telangiectasia is rare, occurring in approximately one in 5000-10,000 people. As the name suggests, this condition is inherited. A person who has HHT has a 50 per cent chance of passing it on to their child. However, the severity of symptoms varies considerably between individuals.
Problems associated with HHT
Generally, people with hereditary haemorrhagic telangiectasia, also known as Osler-Weber-Rendu syndrome, have a history of recurrent nosebleeds.
Small AVMs known as telangiectases also occur in the skin (especially on the fingers, hands, face and lips), the tongue and lining of the mouth and nose, and the conjunctiva (the thin, transparent membrane that covers your eyes). Typically they appear as small red or purple dots that grow slowly in size, although the size can vary from barely visible to up to 1 cm across. The telangiectases appear progressively from late childhood into middle age. Bleeding from these lesions rarely causes problems.
Larger AVMs may occur in organs such as the lungs, liver and brain — these AVMs can cause problems if they bleed. People with hereditary haemorrhagic telangiectasia may also have AVMs in the lining of the bowel or the bladder that can also bleed, and may lead to the development of anaemia. Bleeding from the gastrointestinal tract tends to occur in older people with HHT.
The diagnosis of hereditary haemorrhagic telangiectasia is based on the symptoms as well as genetic testing, which is available through specialised centres.
Doctors use certain criteria to diagnose HHT, which include:
- recurrent nosebleeds;
- multiple telangiectases in typical areas (such as the face, mouth, nose, hands);
- AVMs that involve internal organs; and
- a family history of HHT.
A definite diagnosis requires 3 out of 4 criteria; 2 out of 4 means the disorder is suspected; while having only one criteria makes the diagnosis of HHT unlikely.
Anyone who has been diagnosed as definitely having this disease should have a brain scan to check for AVMs. This is because there are usually no symptoms associated with an AVM in the brain until it bleeds, possibly having serious consequences. Either an MRI scan or a CT scan can detect these lesions. People with hereditary haemorrhagic telangiectasia often also have a scan to check for AVMs in the lungs and liver.
Most people with this condition will only be mildly affected, but regular medical check-ups twice a year, as well as early treatment for any symptoms that might develop, are recommended.
Iron supplements may be needed because of ongoing blood loss.
If scans reveal AVMs in the brain or the lungs, the decision to have them treated depends on a number of factors, such as the site of the lesion, the risks of treatment and the age of the person.