1. Nosebleeds (epistaxis), which are spontaneous and recurrent, may be mild or severe.

2. Telangiectases on the skin or mucous membranes (mucocutaneous). Telangiectases are small red spots that blanch under pressure, located at characteristic sites, including the lips, oral cavity, fingers, and nose.

3. Visceral arteriovenous malformations (AVMs) consisting of direct connections between arteries and veins. They may be located in the lungs, brain, liver, spinal cord, or GI tract.

4. A first-degree relative (brother, sister, parent or child) with HHT, based on these diagnostic criteria.