Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) glycogen storage disease type VII ?
    ### Response:
    Glycogen storage disease type VII (GSDVII) is an inherited disorder caused by an inability to break down a complex sugar called glycogen in muscle cells. A lack of glycogen breakdown interferes with the function of muscle cells.  There are four types of GSDVII.
    