Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) sialic acid storage disease ?
    ### Response:
    Sialic acid storage disease is an inherited disorder that primarily affects the nervous system. People with sialic acid storage disease have signs and symptoms that may vary widely in severity. This disorder is generally classified into one of three forms: infantile free sialic acid storage disease, Salla disease, and intermediate severe Salla disease.
    