Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Neurofibromatosis ?
    ### Response:
    The neurofibromatoses are genetic disorders that cause tumors to grow in the nervous system. The tumors begin in the supporting cells that make up the nerves and the myelin sheath--the thin membrane that envelops and protects the nerves. These disorders cause tumors to grow on nerves and, less frequently, in the brain and spinal cord, and produce other abnormalities such as skin changes and bone deformities.
    