Hereditary hemorrhagic telangiectasia (HHT or Osler-Weber-Rendu disease) is an autosomal dominant disorder of blood vessel formation affecting 1/8000-1/10,000 people. Abnormal direct connections of arteries and veins in larger vessels manifest as arteriovenous malformations (AVMs) most often in the lungs, liver, and brain. Genetic testing enables: confirmation of diagnosis of HHT in symptomatic individualsdetermination of disease status in at-risk family membersearly detection of AVMsopportunity for management to prevent or minimize complications of HHT