Below is an instruction from Human. Write a response.
    ### Instruction:
    What causes Behcet's disease ?
    ### Response:
    What causes Behcet's disease? The exact cause of Behet's disease is unknown. Most symptoms of the disease are caused by inflammation of the blood vessels. Inflammation is a characteristic reaction of the body to injury or disease and is marked by four signs: swelling, redness, heat, and pain.
    