Below is an instruction from Human. Write a response.
    ### Instruction:
    What causes Henoch-Schnlein Purpura ?
    ### Response:
    Henoch-Schnlein purpura is caused by an abnormal immune system response in which the bodys immune system attacks the bodys own cells and organs. Usually, the immune system makes antibodies, or proteins, to protect the body from foreign substances such as bacteria or viruses.
    