Below is an instruction from Human. Write a response.
    ### Instruction:
    What causes Schnitzler syndrome ?
    ### Response:
    What causes Schnitzler syndrome? The exact underlying cause of Schnitzler syndrome is currently unknown. People affected by this condition often have a blood abnormality called monoclonal gammopathy, a condition in which the body over-produces certain immunoglobulins (typically immunoglobulin M).
    