Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Troyer syndrome ?
    ### Response:
    Troyer syndrome 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). Hereditary spastic paraplegias are divided into two types: pure and complex.
    