Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Potassium aggravated myotonia ?
    ### Response:
    Potassium aggravated myotonia is a group of diseases that causes tensing and stiffness (myotonia) of skeletal muscles, which are the muscles used for movement.  The three types of potassium-aggravated myotonia include myotonia fluctuans, myotonia permanens, and acetazolamide-sensitive myotonia.
    