Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Tay-Sachs disease ?
    ### Response:
    Tay-Sachs disease is a rare inherited disorder that progressively destroys nerve cells (neurons) in the brain and spinal cord.  The most common form of Tay-Sachs disease becomes apparent in infancy. Infants with this disorder typically appear normal until the age of 3 to 6 months, when their development slows and muscles used for movement weaken.
    