Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) spastic paraplegia type 15 ?
    ### Response:
    Spastic paraplegia type 15 is part of a group of genetic disorders known as hereditary spastic paraplegias. These disorders are characterized by progressive muscle stiffness (spasticity) and the development of paralysis of the lower limbs (paraplegia). Spastic paraplegia type 15 is classified as a complex hereditary spastic paraplegia because it involves all four limbs as well as additional features, including abnormalities of the brain.
    