Below is an instruction from Human. Write a response.
    ### Instruction:
    What causes Bethlem myopathy ?
    ### Response:
    What causes Bethlem myopathy? Bethlem myopathy is caused by mutations in the COL6A1, COL6A2, and COL6A3 genes. These genes each provide instructions for making one component of a protein called type VI collagen. This protein plays an important role in muscle, particularly skeletal muscle.
    