The abnormal HHT gene 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% chance of inheriting this abnormal gene.
If a particular child does not inherit the HHT gene from his or her parent, he/she has no chance to pass the HHT gene to a child or grandchild. The gene does not skip generations. However, sometimes it can appear to skip because an individual with an HHT gene has symptoms that are so mild that they aren t recognized, or if recognized are not correctly attributed to HHT.
There are several tests that everyone who is known or suspected to have HHT should have. Since lung and brain AVMs can cause serious damage without warning, and they can be successfully treated, testing is strongly suggested for these. Testing for brain and lung AVMs is often referred to as "screening", meaning the AVM is looked for prior to causing a problem.
To screen for brain AVMs an MRI with and without gadolinium is recommended. It is currently recommended that a brain MRI only needs to be done once early in life and once as an adult, if it is normal.
Most brain AVMs are thought to be congenital (present at birth).
Wilma CogliantryWilma Cogliantry - Hereditary Hemorrhagic Telangiectasia- Arterial Venous Malformation. Each child of a parent with an HHT gene has a 50% chance of inheriting this abnormal gene. If a particular child does not inherit the HHT gene from his or her parent, he/she has no chance to pass the HHT gene to a child or grandchild. The gene does not skip generations. However, sometimes it can appear to skip because an individual with an HHT gene has symptoms that are so mild that they aren't recognized, or if recognized are not correctly attributed to HHT. Wilma Cogliantry of Christian Lane Quilters had brain surgery for an AVM. She believes she inherited the gene from her mother. (HHT) is a genetic disorder of the blood vessels, which affects approximately 1 in 5,000 people. The abnormal HHT gene 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. Before Dr. Rendu's work, doctors did not understand that individuals with what we now call HHT have abnormalities of their blood vessels, not a clotting problem in the blood itself. Drs. Weber and Osler reported on additional features of HHT in the early 1900s. More than one hundred years later, HHT is still often misdiagnosed in affected individuals and many doctors do not understand all of its manifestations. 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. 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 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. HHT can be treated. Although there is not yet a way to prevent the telangiectases or AVMs from occurring, most can be treated once they occur. They should be treated if they are either causing a significant problem (as in the case of frequent nosebleeds) or if they are at high risk of causing a serious problem (such as a stroke from a lung AVM.) The recommended treatment for a telangiectasia or AVM depends on both its size and location in the body. 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. Brain AVMs 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. Genetic testing for HHT is available, but it needs to be preceded by a clinical confirmation of HHT in your family. This is because the genetic testing for HHT must first be run on a clearly affected person in your family. Results from these genetic tests results HHT will determine whether it is useful to test other family members who want to know whether they have HHT. Many individuals who initially request a genetic test for HHT actually do not need this expensive test to determine whether they have HHT. In many cases a physician familiar with the sometimes-subtle external signs of HHT, and who takes a detailed family history, can make the diagnosis during a clinic visit. The following Diagnostic Criteria for HHT have been published by an international group of HHT experts. The diagnosis of HHT is considered definite if three or more of the following four criteria are present, or suspected if two of the following four criteria are present: * Nosebleeds- spontaneous and recurrent * Telangiectases- multiple, at characteristic sites, including lips, fingers and nose Internal telangiectases or AVM- lung, brain, GI, liver or spinal * Family history-parent, sibling or child with HHT according to these criteria. To establish the diagnosis of HHT in your family, and to proceed with genetic testing as needed it is usually best to be seen at an HHT Center, or a genetics clinic in your area. Physicians or genetic counselors in these clinics will understand the process and particulars of how best to determine whether you and/or members of your family have HHT, including genetic testing. The youngest individuals in an HHT family are typically the most helped by genetic testing, but testing usually must start with a parent or grandparent. There are several tests that everyone who is known or suspected to have HHT should have. Since brain AVMs can cause serious damage without warning, and they can be successfully treated, testing is strongly suggested. Testing for brain AVMs is often referred to as "screening", meaning the AVM is looked for prior to causing a problem. To screen for brain AVMs an MRI with and without gadolinium is recommended. It is currently recommended that a brain MRI only needs to be done once early in life and once as an adult, if it is normal. Most brain AVMs are thought to be congenital (present at birth). Lung and brain AVMs are the only problems associated with HHT for which pre-symptomatic screening is routinely recommended. Most insurance companies will pay for these recommended screening tests if a brief explanation of the association between HHT and AVMs in these internal organs is provided. Other than in the brain and lungs, HHT can be treated as symptoms warrant.
