Below is an instruction from Human. Write a response.
    ### Instruction:
    What causes Peripheral Artery Disease ?
    ### Response:
    The most common cause of peripheral arterydisease (P.A.D.) is atherosclerosis. Atherosclerosis is a disease in which plaque builds up in your arteries. The exact cause of atherosclerosis isn't known.
                
The disease may start if certain factors damage the inner layers of the arteries.
    