HHT is a genetic disorder – a change in the genes causes HHT. We inherit half of our genes from each of our parents. When a gene change occurs, there is the potential that this can cause problems with health. HHT occurs when there is a change in the genes that control the development of blood vessels.

AVMs or arteriovenous malformations occur when an artery develops an abnormal connection straight to a vein. Normally blood travels from the heart in arteries and then gets to body organs and tissues by dividing into very small blood vessels called capillaries. The capillaries then drain into veins which carry the blood back to the heart. An AVM occurs when the blood travels straight from the arteries to the vein.

The abnormal connection between the artery and the vein is often very fragile and can rupture or burst leading to bleeding into the tissues.

The type of symptoms that a ruptured AVM causes will depend on where the AVM occurs in the body.

• AVMs can occur in the skin (called telangiectasia), in the lining of the nose (can cause severe blood noses), in the brain (cause strokes) and in the lungs (cause bleeding into the lungs).
• Less commonly, AVMs can occur in the liver and the gastrointestinal tract.

HHT can be diagnosed by taking a careful family history to identify relatives who may have had HHT, by close examination to see if patients have AVMs and by specialised radiology or imaging studies to see if AVMs are present in organs in the body.

There is also specialised genetic test that can be performed to identify the gene changes that are responsible for HHT.

The type of specialised radiology tests for each of the different types of AVMs is listed below.

Management of blood noses

The management of blood noses (epistaxis) in patients with HHT can be difficult. Epistaxis is very common in HHT with approximately 50% of patients with HHT experiencing epistaxis as a child / adolescent. Epistaxis is common in HHT due to the presence of abnormally fragile vessels in lining of the nose.

A number of treatments are available including keeping these blood vessels moist (e.g. humidification or applying a lubricant), minor surgical procedures to remove the blood vessels (e.g. cauterisation) or even applying a skin graft to the area to stop the bleeding (septodermoplasty).

It is important that the doctors dealing with the blood noses are familiar with HHT since some procedures can lead to more bleeding.

HS is relatively common – around 1 person in every 5000 people has HS (around 800 people in Melbourne; population 4 million).

There are three main common problems associated with having HS:

There is another uncommon potential problem for people who have Hereditary Spherocytosis associated with a viral infection called “Slapped cheek”. Slapped cheek is caused by a virus called Parvovirus which can infect bone marrow cells and put the red cell producing cells “to sleep”. Because patients with HS need the bone marrow to be rapidly replacing the fragile red cells, this infection can cause a severe anaemia; patients can become very pale and sometimes even require blood transfusions. Fortunately this problem is uncommon.

HS is now diagnosed with a simple blood test. It is also important for a doctor to examine patients with HS to see if they are jaundiced or have an increase in the size of the spleen.

Most patients with HS do not need to do much about their condition at all. The bone marrow has the capacity to increase the number of red cells it produces many fold and is able to keep up replacing the fragile cells.

A few things may be helpful:

Removing the spleen (splenectomy) has been used a lot in the past in the treatment and management of patients with HS; it stops the red cells from breaking down and solves the problems of HS.

Removing the spleen has problems however – the spleen is an important organ in the immune system and patients who do not have a spleen may be prone to getting serious infections. This risk is higher in younger children but may be less than previously expected because of newer vaccinations. It is now generally recommended to avoid splenectomy in children younger than 6 years and to ensure that children who may need a splenectomy have all the appropriate vaccinations.

Another approach for some of these young patients is to remove only a small part of the spleen – partial splenectomy. This is done in a few hospitals and there is some experience to say this may be very helpful for some patients.