Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Silver syndrome ?
    ### Response:
    Silver syndrome belongs to a group of genetic disorders known as hereditary spastic paraplegias. These disorders are characterized by progressive muscle stiffness (spasticity) and, frequently, development of paralysis of the lower limbs (paraplegia). Hereditary spastic paraplegias are divided into two types: pure and complex.
    