Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) familial dysautonomia ?
    ### Response:
    Familial dysautonomia is a genetic disorder that affects the development and survival of certain nerve cells. The disorder disturbs cells in the autonomic nervous system, which controls involuntary actions such as digestion, breathing, production of tears, and the regulation of blood pressure and body temperature.
    