What is HHT? Home » Understanding HHT » What is HHT HHT affects more than 1.4 million people worldwide. Hereditary Hemorrhagic Telangiectasia (HHT) is a genetic disorder that causes malformed blood vessels and can affect multiple organs of the body. The disorder is also sometimes referred to as Osler-Weber-Rendu (OWR) after several doctors who studied … Continue reading What is HHT