Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Microscopic polyangiitis ?
    ### Response:
    Microscopic polyangiitis (MPA) is a disorder that causes blood vessel inflammation (vasculitis), which can lead to organ damage. The kidneys, lungs, nerves, skin, and joints are the most commonly affected areas of the body. MPA is diagnosed in people of all ages, all ethnicities, and both genders.
    