Below is an instruction from Human. Write a response.
    ### Instruction:
    What causes Parsonage Turner syndrome ?
    ### Response:
    What causes Parsonage Turner syndrome? The exact cause of Parsonage Turner syndrome (PTS) is unknown. Researchers suspect that most cases are due to an autoimmune response following exposure to an illness or environmental factor. In many cases, no triggering event or underlying cause can be identified.
    