Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) spastic paraplegia type 3A ?
    ### Response:
    Spastic paraplegia type 3A is one of a group of genetic disorders known as hereditary spastic paraplegias. These disorders are characterized by muscle stiffness (spasticity) and weakness in the lower limbs (paraplegia). Hereditary spastic paraplegias are often divided into two types: pure and complex.
    