HHT Quick 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.

Untreated pulmonary AVMs are a common cause of ischemic stoke and brain abscess in HHT families.

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, but is complex. 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 Center.