Hereditary Hemorrhagic Telangiectasia (HHT), also known as Osler-Weber-Rendu Syndrome, is a rare genetic disorder that affects blood vessels and creates symptoms of bleeding and haemorrhage. HHT is often misdiagnosed because it masquerades as many disorders. Most people with HHT, by the time they are in their 30's, will have telangiectases, which are red spots, often found on the lips, tongue, fingers, or toes. These telangiectases may bleed occasionally. About 90% of people who have HHT will have nosebleeds. These may be frequent enough to require transfusions. About a third of people with HHT will have gastrointestinal bleeding, which can also require frequent transfusions. Perhaps a quarter of people with HHT have pulmonary arteriovenous malformations (PAVMs) which can lead to serious complications such as stroke and brain abscess or shortness of breath. About 20% of people with HHT have cerebral arteriovenous malformations (CAVMs) which can cause haemorrhagic stroke. Other less common manifestations of HHT can include arteriovenous malformations in the liver or spinal cord.
HHT is an autosomal dominant disorder, which means that a child of either sex born to a person with HHT has a 50% chance of inheriting the responsible gene and thus having HHT. Children who do not inherit the gene will not be affected nor will they pass the gene on to their children.