Hereditary hemorrhagic telangiectasia: A genetic disease characterized by the presence of multiple direct connections between arteries and veins called arteriovenous malformations (AVMs). Small AVMs, or telangiectases, close to the surface of skin and mucous membranes often rupture and bleed after slight trauma. Abbreviated HHT. The most common manifestations of HHT are recurrent nosebleeds beginning at about 12 years of age. About one-fourth of individuals with HHT will develop gastrointestinal bleeding. Large AVMs may also bleed in the brain, lung, or other sites. HHT is inherited as an autosomal dominant trait. Most patients have a parent with HHT. HHT is unusual in that it can be caused by a mutation in at least three different genes. Also known as Osler-Rendu-Weber syndrome and Rendu-Osler-Weber syndrome.