What is HHT? – Hereditary Haemorrhagic Telangiectasia.
According to CureHHT:
“HHT is a genetic disorder that causes abnormalities of blood vessels. Most blood vessels in the body of someone with HHT are normal. However, a small percentage of the blood vessels in a person with HHT have a specific type of abnormality.
Blood vessels are the tubes that carry blood around our bodies. There are two types of blood vessels: arteries and veins. Arteries carry blood under high pressure out to all areas of the body after being pumped by the heart. Veins carry blood that should be under low pressure, back to the heart. An artery does not usually connect directly to a vein. Usually there are very small blood vessels called capillaries that connect an artery to a vein.
Note: Also known as Osler-Weber-Rendu Syndrome
A person with HHT has a tendency to form blood vessels that lack the capillaries between an artery and vein. This means that arterial blood under high pressure flows directly into a vein without first having to squeeze through the very small capillaries. This place where an artery is connected directly to a vein tends to be a fragile site that can rupture and result in bleeding. We usually call a blood vessel that is abnormal in this way a telangiectasia (tel-AN-jee-eck-TAZE-ee-ya), if it involves small blood vessels. We tend to call it an arteriovenous malformation (AVM) if it involves larger blood vessels. So, an AVM might be thought of as a big telangiectasia. The basic abnormality in the blood vessel is the same.
Telangiectases tend to occur at the surface of the body such as the skin and the mucous membrane that lines the nose. AVMs tend to occur in the internal organs of the body. The telangiectases (plural for telangiectasia) and AVMs of HHT occur primarily in the nose, skin of the face, hands, and mouth and the lining of the stomach and intestines (GI tract), lungs, liver and brain. It is not currently known why these abnormal blood vessels tend to occur in certain parts of the body and not others.
About 95% of people with the gene for HHT will eventually develop signs or symptoms of HHT, usually by the age of 40. However, just because a person reaches the age of 50 without symptoms of HHT does not mean that they are not affected. They may have subtle signs on physical exam and lab testing that only a doctor familiar with HHT might detect. The earliest symptom of HHT is usually nosebleeds, often developing in adolescence. Patients also start to develop small red spots, or telangiectasias, on the face, mouth, fingers, and in the gastrointestinal tract. A high number of HHT patients will also have or develop artery malformations (AVMs) in one or more body organs, where capillaries between arteries and veins are missing. These can cause mild to life threatening complications and, because they are hidden, make HHT one of the most challenging diseases to diagnose.
Other common symptoms of HHT include:
- Telangiectasias (more information below)
- Shortness of breath
- Exercise intolerance
- Migraine headaches
- Abdominal pain
- Leg swelling
- Intestinal bleeding
- Artery Malformations (more information below)
The Epistaxis Severity Score (ESS) is a way to monitor the severity of your nosebleeds and their response to treatment. This is a simple score that is calculated automatically from six simple questions about your nosebleeds. You can access the ESS tool here.
Nose Telangiectasias – Telangiectasias in the nose, along with the nosebleeds they cause, are the most common sign of HHT. About 90% of people with HHT will ultimately develop recurring nosebleeds by the time they reach their forties. The average age at which nosebleeds begin is 12, but they can begin as early as infancy, or as late as adulthood. The nosebleeds can be as infrequent as a few times a year or can occur daily. When a nosebleed occurs it can last anywhere from seconds to hours. The amount of blood lost may be one or two drops, or enough to require an emergency blood transfusion.
Hands, Face & Mouth Telangiectasias – Telangiectasias on the skin of the hands, face and mouth are also found in about 95% of all people with HHT. However, these often do not become apparent until the 30’s or 40’s. They appear as small red to purplish spots, usually pinpoint to pinhead size. In some individuals with HHT they become quite prominent by late adulthood; in others they are more subtle. These telangiectasias on the hands, face or in the mouth can bleed, but they are less likely to bleed than those in the nose. Both telangiectasias of the skin and nose have a tendency to become more numerous with increased age. However, not all red spots are telangiectasias. Red spots on the chest, belly or upper arms are common in people without HHT and are usually called cherry angiomas.
- Stomach & Gastrointestinal System Telangiectasias – About 80% of those with HHT have telangiectasias in their stomach or intestines, but only 20% develop obvious gastrointestinal bleeding, ranging from mild to severe. Telangiectasias can be found anywhere in the gastrointestinal system, including the esophagus,stomach, small intestines, and colon (large intestines), but most commonly, the stomach and the upper part of the small intestines are involved. Telangiectasias in the GI tract do not cause pain or discomfort. Symptoms of GI bleeding are black or bloody stools and/or anemia; often patients don’t notice any change in the stool but instead are found anemic through blood work. Anemia can cause fatigue, shortness of breath, chest pain or lightheaded feelings.
Artery Malformations (AVMs)
What is an AVM? An arteriovenous malformation (AVM) is an abnormality in the larger blood vessels.
Lung AVMs – Approximately 40% of people with HHT have AVMs in the lungs (pulmonary AVM or PAVM for short). People with the genetic variation HHT1 (ENG) are 5-10 times more likely to have PAVMs than people with HHT2 (ACVRL1). PAVMs, particularly during pregnancy, have a risk of rupturing when blood volume tends to increase. This can be life-threatening. However, there are additional concerns about untreated PAVMs. Normally, the lung arteries get smaller and smaller as they go deeper into the lungs, similar to the branches of a tree. At the ends of these artery branches, hair- like blood vessels called capillaries join the arteries and veins. These capillaries perform many important functions including allowing passage of oxygen into the blood as well as filtering the blood of impurities (clots, bacteria, air bubbles) before the blood circulates to the brain. With a PAVM, these capillaries are missing and the artery connects directly to the vein. If the artery leading into the PAVM is larger than 2-3 mm in diameter, small blood clots can travel through the PAVM and go to the brain causing a stroke. Bacteria can travel through even smaller PAVMs and result in brain abscesses (a brain infection). Stroke and brain abscess can be life-threatening or disabling. Fortunately, PAVMs are almost always easily treatable. PAVM – Where the AVM exists in the Pulmonary area ie lungs – it is called a PAVM. PAVMs can almost always be treated completely and permanently using an outpatient procedure called embolization. An Interventional Radiologist inserts a small tube (catheter) in a large vein in the groin. The tube is then passed through the blood vessel system to the AVM in the lung. A devise (a coil or occasionally a balloon) is placed in the artery leading to the AVM to stop blood flow through the AVM. The procedure usually takes 1-3 hours and requires only a few hours of recuperation.
Brain AVMS are found in about 5-20% of people with HHT and can also be successfully treated in most cases. They can be life-threatening or disabling if they bleed. Since they often do not cause warning symptoms prior to bleeding, we recommend screening for them in all people with HHT, even infants. Other types of brain vascular malformations may be seen in HHT patients, such as telan- giectasias and vein malformations. It is not clear if these malformations are seen any more commonly in HHT patients, but they are usually harmless and most do not require treatment. CAVM – Where the AVM exists in the brain – it is called a CAVM (Cerebral AVM). CAVMs are treated in different ways depending on the size, structure and location in the brain of the abnormal blood vessels. Surgery, embolization and stereotactic radiosurgery can all be used, separately or in combination, to successfully treat brain AVMs.
Spinal AVMs are more rare, less than 1%, but can also be treated. They can cause pain in the area of the back over the spine, or loss of feeling or function in an arm or leg.
Liver AVMs are found in 32-74% of people with HHT, but only cause symptoms in an estimated 8%. AVMs in the liver occasionally cause heart failure, usually later in life. Heart failure can occur if the heart has been overworked for years, pumping extra blood through the low resistance pathway of a liver AVM (shunt), as well as through all the normal vessels of the body. There are several other even more rare and complex complications that can result when HHT affects the liver. Few physicians outside of clinics that specialize in HHT are familiar with these complications. Liver AVMs are currently treated only if a patient shows signs of liver or heart failure, as a result of their liver AVM. Embolization, which is so successful for the treatment of pulmonary AVMs, can cause severe complications when performed in the liver. Decisions regarding treatment of liver AVM are made on a case-by-case basis and should be managed by a physician very familiar with the liver manifestations of HHT.