Behçet’s disease is a rare immune system disorder that causes inflammation in various parts of the body. People with Behçet’s (pronounced buh-CHETS) disease have recurrent, painful ulcers in the mouth and sometimes on the genitals, as well as lesions on the skin. More serious symptoms include inflammation in the eyes, the brain, or both; a bulge in the wall of an artery in the lungs, called an aneurysm; and obstruction of blood vessels. Behcet’s is considered a type of vasculitis, because it causes inflammation of blood vessels of nearly all sizes and types, including arteries and veins.