Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Paramyotonia congenita ?
    ### Response:
    Paramyotonia congenita is an inherited condition that affects muscles used for movement (skeletal muscles), mainly in the face, neck, arms, and hands. Symptoms begin in infancy or early childhood and include episodes of sustained muscle tensing (myotonia) that prevent muscles from relaxing normally and lead to muscle weakness.
    