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The Facts about HHT

HHT at a Glance

What is HHT ? HHT is a genetic disorder of the blood vessels.

Diagnosis and treatment - HHT has changed significantly in the last decade. Recommended screening and treatment (if, when, and how) is dramatically different for pulmonary vs. cerebral vs. hepatic AVMs. The HHT Foundation recommends that people with HHT be assessed at least once, as early in life as possible, at a specialized HHT Centre.

General Information about HHT

  1. Hereditary Hemorrhagic Telangiectasia (also known as Osler-Weber-Rendu Syndrome) is a multi-system vascular dysplasia.
  2. Approximately 1.4 million people world-wide have HHT which is uncommon, but not rare.
  3. Telangiectases and arteriovenous malformations (AVMs) are the characteristic lesions.
  4. Location of lesions and severity of symptoms is highly variable and is significantly under diagnosed in affected individuals.
  5. Symptoms can be mild to severe.
  6. Physicians frequently miss (do not make) the diagnosis in affected individuals.
  7. Most commonly affected organs are the nose, lungs, GI tract, brain, and liver.
  8. HHT is an autosomal dominant genetic disorder. Denovo mutations are rare. A targeted family history shows almost all cases to be familial.
  9. HHT is heterogenic with defects in at least 3 different genes.
  10. The severity of one's nosebleeds (epistaxis) or skin telangiectasias does not correlate with the likelihood of having brain or lung AVMs.
  11. Untreated brain AVMs are a common cause of hemorrhagic stroke in HHT families.
  12. Severity of the disorder varies tremendously, even between close relatives.
  13. Treatments are available for all manifestations of HHT.
  14. Men and women are affected with HHT in equal numbers.

HHT Manifestations

  1. 90-95% of individuals with HHT will have nosebleeds by adulthood, but severity varies from infrequent and minor to daily and severe.
  2. 90-95% develop at least a few telangiectasia (small red or purple spots) on the skin of the face and/or hands by middle age.
  3. 20-25% develop significant gastric or intestinal bleeding, but rarely before 50 unless affected with juvenile polyposis in conjunction with HHT.
  4. 40% have lung AVMs. These pose significant risk.
  5. 5-20% have at least one brain AVM. These can be present at any time in life, even at birth, and can cause serious complications. Routine screening is recommended in North American centers.
  6. Liver AVMs are relatively common, but only approximately 10% cause symptoms.
  7. Abnormal blood vessels in the liver are relatively common, but most cause no symptoms. Biopsy or treatment should rarely be done and specifically, embolization should not be done.

Lung AVMs

The following precautions are recommended for all HHT patients with lung AVMs (treated and untreated), as well as those not yet screened by an HHT Center of Excellence.

  • Antibiotic Prophylaxis is recommended for dental and other procedures that can cause bacteria in the blood.
  • IV Filter - An IV air filter (bubble trap) should be used when a patient has an intravenous line. This is to prevent any large air bubble from entering the bloodstream, going through a lung AVM, and then causing a temporary stroke. This is most effectively done by using a filter in the IV line as close to the patient as possible. A 0.22 micron filter is best, if available, but a blood filter is also acceptable (about 260 microns) and will stop all large air bubbles. During a blood transfusion, a standard blood filter is all that is needed. Please note that filters often cannot be used for IV contrast injections like you might get for CT or MRI scans.

Epistaxis Severity Scoring Tool (ESS)

This is a way to monitor the severity of a patients' nosebleeds and their response to treatment. This is a simple score that is calculated automatically when the patient answers 6 simple questions about their nosebleeds. Online ESS Tool.

Quick Medical HHT Facts for Health Care Professionals

• Hereditary Hemorrhagic Telangiectasia (AKA Olser-Weber-Rendu) is a multi-system vascular dysplasia. It is uncommon, but not rare. Approximately 1.2 million people worldwide have HHT.
• Telangiectases and arteriovenous malformations (AVMs) are the characteristic lesions.
• Location of lesions and severity of symptoms is highly variable and it is significantly under diagnosed in affected individuals.
• Most commonly affected organs are the nose, lungs, GI tract, brain, liver and spine in that order.
• HHT is an autosomal dominant genetic disorder. Denovo mutations are rare. A targeted family history shows almost all cases to be familial.
• HHT is heterogenic. Defects in at least 3 genes cause HHT.
• 90-95% of individuals with HHT will develop epistaxis by adulthood, but severity varies from infrequent and minor to daily and severe.
• 90-95% develop at least a few small telangiectasia on the face and/or hands by middle age.
• 20-25% develop significant gastric or intestinal bleeding, but rarely before 50 unless affected with juvenile polyposis in conjunction with HHT.
• 30-50% have pulmonary arteriovenous malformation (AVM). These are largely congenital and pose significant risk.
• 5-20% have at least one cerebral AVM. These are congenital and pose significant risk.
• Hepatic AVM are relatively common, approximately 5% are symptomatic.
• The severity of epistaxis or dermal telangiectases does not correlate with the likelihood to have cerebral or pulmonary AVMs.
• Antiobiotic Prophylaxis for dental and other "dirty" procedures, such as tatooing, are strongly recommended in all HHT patients with PAVMs in order to prevent bacteria from entering the blood stream which can lead to a brain abscess.

Pulmonary AVMs - A .22 micron IV Filter is recommended for all HHT patients with known PAVMs, untreated PAVMs, or those not yet screened by an HHT Center of Excellence. Untreated pulmonary AVMs are a common cause of ischemic stroke and brain abscess in HHT families.
Cerebral AVMs - Untreated cerebral AVMs are a common cause of hemorrhagic stroke in HHT families.
Recommended screening and treatment (if, when and how) is dramatically different for pulmonary vs. cerebral vs. hepatic AVMs. For example, transcatheter embolization - safe and effective treating for pulmonary AVMs - should almost never be used to treat hepatic AVMs since infarction frequently results.
Molecular genetic testing for HHT is now available in a handful of labs worldwide. Since genetic testing for HHT is a multi-step, multi-generation process, it is usually best coordinated by a medical geneticist or genetic counselor. Testing an individual suspected to have HHT, without first testing a clinically affected family member is rarely informative.
Diagnosis and treatment for HHT has changed significantly in the last decade. The HHT Foundation recommends that people with HHT be assessed at least once at a specialized HHT Centre of Excellence

Learn more about HHT Click here

RESOURCES (from Curehht.org)
https://curehht.org/resource-library/

SCHOOLS GUIDE PDF
http://hhtireland.org/images/SchoolsGuideJune2018.pdf

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