Below is an instruction from Human. Write a response.
    ### Instruction:
    What causes Troyer syndrome ?
    ### Response:
    What causes Troyer syndrome? Troyer syndrome is caused by mutations in the SPG20 gene. This gene gives the body instructions to make a protein called spartin, which is present in many body tissues, including those of the nervous system. However, the function of this protein is not fully understood.
    