Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Sandhoff disease ?
    ### Response:
    Sandhoff disease is a rare inherited disorder that progressively destroys nerve cells (neurons) in the brain and spinal cord.  The most common and severe form of Sandhoff 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.
    