Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Hereditary Spastic Paraplegia ?
    ### Response:
    Hereditary spastic paraplegia (HSP), also called familial spastic paraparesis (FSP), refers to a group of inherited disorders that are characterized by progressive weakness and spasticity (stiffness) of the legs. Early in the disease course, there may be mild gait difficulties and stiffness.
    