Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Pompe disease ?
    ### Response:
    Pompe disease is an inherited disorder caused by the buildup of a complex sugar called glycogen in the body's cells. The accumulation of glycogen in certain organs and tissues, especially muscles, impairs their ability to function normally.  Researchers have described three types of Pompe disease, which differ in severity and the age at which they appear.
    