Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) tubular aggregate myopathy ?
    ### Response:
    Tubular aggregate myopathy is a disorder that primarily affects the skeletal muscles, which are muscles the body uses for movement. This disorder causes muscle pain, cramping, or weakness that begins in childhood and worsens over time. The muscles of the lower limbs are most often affected, although the upper limbs can also be involved.
    