Common Childhood Conditions
Hereditary Hemorrhagic Telangiectasia
What Does Hereditary Hemorrhagic Telangiectasia (HHT) Look Like?
A child with HHT, also known as Osler-Weber-Rendu Syndrome, tends to form blood vessels that lack the capillaries between an artery and vein.
Capillaries are very small blood vessels where arteries drop off their oxygen and then flow into veins (large blood vessels without oxygen).
In this condition, without capillaries, arterial blood under high pressure flows directly into a vein. This pressure tends to rupture the vessels and result in bleeding.
Telangiectases often occur at the surface of the body, such as the skin and the mucous membrane that lines the nose.
When HHTs involve larger blood vessels they can be found inside the body and are called
arteriovenous malformations (AVMs)
AVMs can have other causes, but the telangiectases and AVMs of HHT occur mostly in the following areas:
- Skin of the face, hands and mouth
- Lining of the stomach and intestines (GI tract), lungs and brain
What Causes HHT and Who Gets It?
An abnormal gene on either chromosome 9 or 12 causes HHT and is usually inherited from one parent who has HHT.
HHT is a "dominant" disorder, meaning it only takes one abnormal copy of the gene, from only one parent, to cause the disorder.
Each child of a parent with an HHT gene has a 50 percent chance of inheriting this abnormal gene.
It is estimated that 1 in every 5,000 people worldwide have HHT.
What Are the Signs and Symptoms of HHT?
Since telangiectases in the nose is the most common type, nosebleeds are the most common signs of HHT. About 95 percent of people with HHT have severe daily to weekly nosebleeds by the time they reach middle age.
Telangiectases in the skin of the hands, face and mouth are also found in about 95 percent of all people with HHT. These do not become apparent until the 30s or 40s. These telangiectases on the skin and in the mouth can bleed also, but they are less likely to than those in the nose.
About 25 percent of those with HHT will develop stomach or intestine (GI) bleeding that can range from mild to severe. Signs of stomach bleeding are vomiting blood or dark, tarry stools.
About 30 percent of people with HHT have one or more AVMs in the lungs marked by coughing up blood. AVMs in the lungs are at risk of rupturing, especially during pregnancy. Someone with a lung AVM above a certain size is at significant risk for stroke or brain abscess. Fortunately, lung AVMs are often easily treatable.
Brain AVMs are found in about 15 percent of people with HHT. They can be life-threatening or disabling if they bleed. With proper screening, these can also be successfully treated in most cases.
How Will Seattle Children's Diagnose HHT?
Family history is a primary key to diagnosing HHT. We look at the child's parents. If one parent has HHT, the child should be carefully watched and screened with pulse oximetry every two or three years to detect pulmonary AVMs.
Genetic testing for HHT became available in late 2003. It is a very complex family testing that should be explained and ordered by a genetics professional. Only a few centers in the United States provide such testing. Children's can help decide if this genetic testing is advisable for your family.
How Will Seattle Children's Treat HHT?
The current recommended treatment for a telangiectasis or AVM connected to HHT depends on both its size and location in your child's body.
Most telangiectasis or AVMs should be treated if they:
- Are causing a problem, such as frequent nosebleeds
- Have a high risk to cause a problem, such as a stroke from a lung AVM
Some of the treatments include but are not limited to:
- Telangiectasis of the nose or skin can be treated with laser therapy.
- Bleeding from the stomach or intestines is generally treated only if it causes anemia (low blood count). Iron replacement therapy is the first line of defense.
- Lung and brain AVMs should be treated before they cause symptoms or problems in most cases. This is why testing or screening for them is recommended in all individuals with HHT, regardless of their specific symptoms.
- Lung AVMs can almost always be treated completely and permanently using an outpatient procedure called embolization.
- Brain AVMs are treated in different ways depending on the size, structure and location in the brain of the abnormal blood vessel. Surgery, embolization and stereotactic radiosurgery can all be used, separately or in combination, to successfully treat brain AVMs.