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08/22/03 |
     
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Hereditary Hemorrhagic Telangiectasis HHTThe following was extracted from HHT International Foundation's web site: - Hereditary Hemorrhagic Telangiectasia (HHT) is a genetic disorder of the blood vessels which affects about one in 10,000 people. It affects males and females from all racial and ethnic groups. 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. 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 call a blood vessel that is abnormal in this way a telangiectasia (tel-AN-jee-eck-TAZE-ee-ya), if it is a small artery attached to a small vein. We call it an arterioveneous malformation (AVM) if it is a larger artery attached to a larger vein. So, an AVM can be thought of as a big telangiectasia, but the basic abnormality in the blood vessel is the same. Telangiectasia 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 telangiectasia and AVM 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 and brain. It is not currently known why they tend to occur in certain parts of the body and not others. Its location in the body determines what problem a telangiectasia or AVM might cause. In most locations, and at any size, a telangiectasia or AVM has greater tendency than a normal blood vessel to rupture and bleed. In the nose, skin, GI tract (stomach and intestines), and brain the primary problem they can cause is bleeding. AVMs in the lungs or liver are often less likely to rupture and bleed, but can cause other problems that are less obvious to doctors and patients who lack an in depth understanding of HHT. No one with HHT has all of the signs and symptoms listed below. One of the very characteristics of HHT is its extreme variability even within a family. A parent may have horrible nosebleeds, but no AVM in an internal organ. Yet, their child may have a nosebleed only rarely but AVMs in one or more internal organ. We also can not predict how likely someone is to have one of the hidden, internal AVMs based on how many nosebleeds or skin telangiectasia they have. Telangiectasia in the nose, along with the nosebleeds they cause, are the most common signs of HHT. About 95% of people with HHT have recurring nosebleeds by the time they reach middle age. 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 once or twice a year, or can occur daily. When a nosebleed occurs it can last only seconds, or occasionally hours. The amount of blood lost may be one or two drops, or enough to require a blood transfusion. As with most things that are variable in human beings (i.e. height and shoe size), the majority of people with HHT are in between the two extremes. Telangictasia in the skin of the hands, face and mouth are also found in about 95% of all people with HHT. These often do not become apparent until the 30s or 40s, however. They appear as small red to purplish spots or distinct areas of delicate, lacy red vessels. In some individuals with HHT they become quite prominent by late adulthood, in others they are subtle. These telangiectasia on the skin and in the mouth can bleed also, but they are less likely to than those in the nose. Both telangiectasia of the skin and nosebleeds have a tendency to become more numerous with increasing age. But with this too, there are many exceptions! About 25% of those with HHT will develop GI bleeding. Again, it can range from mild to severe. Telangiectasia can be found anywhere in the gastrointestinal system, including the esophagus (swallowing tube), the stomach, the small intestines, and the colon (large intestines). Most commonly, the stomach and the beginning of the small intestines are involved. They look similar to telangiectasia on the skin. Telangiectasia in the GI tract do not cause pain or discomfort. Symptoms of GI bleeding are black or bloody stools and/or anemia. Anemia (low blood count) in turn can cause fatigue, shortness of breath, chest pain or lightheaded feelings. Approximately 30% of people with HHT have one or more AVM in the lungs (pulmonary AVM or PAVM). AVMs in the lung have a risk to rupture, particularly during pregnancy in women when blood pressure and blood volume tends to increase. This can be life-threatening. However, there are additional concerns about untreated lung AVMs. The capillaries between an artery and vein in the lung have functions in addition to slowing down the blood in an artery before it enters the vein. These capillaries act as a filter for impurities (clots, bacteria, air bubbles) in the blood, before the blood circulates to the brain. Someone with a lung AVM above a certain size is thus at significant risk for stroke (what happens when a clot goes to the brain) or brain abscess (a brain infection that can result from a bacteria getting to the brain). Stoke and brain abscess can also be life-threatening or disabling. Fortunately, lung AVMs are usually easily and completely treatable. The recommended screening and treatment for them is described below. Brain AVMs are found in about 15% 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 symptoms of warning prior to bleeding, we strongly recommend screening for them in all people with HHT. Spinal AVMs are more rare and can also be removed. They can cause pain in the back over the spine, or loss of feeling or function in an arm or leg. Liver AVMs can also occur, but their frequency in HHT is not well known. They are unlikely to rupture and most are not currently treated. Large AVMs in the liver sometimes cause heart and liver 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 an AVM (in this context an AVM is sometimes called a Shunt), as well as through all the normal vessels of the body.
This site was last updated 05/04/02 |