Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Gerstmann-Straussler-Scheinker disease ?
    ### Response:
    Gerstmann-Straussler-Scheinker disease (GSS) is a type of prion disease, which is a group of conditions that affect the nervous system. Signs and symptoms generally develop between ages 35 and 50 years and may include progressive ataxia, cognitive dysfunction, slurred speech and spasticity.
    