Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) myofibrillar myopathy ?
    ### Response:
    Myofibrillar myopathy is part of a group of disorders called muscular dystrophies that affect muscle function and cause weakness. Myofibrillar myopathy primarily affects skeletal muscles, which are muscles that the body uses for movement. In some cases, the heart (cardiac) muscle is also affected.
    