Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Cramp-fasciculation syndrome ?
    ### Response:
    Cramp-fasciculation syndrome (CFS) is a rare condition of the muscles. Affected people have persistent muscle twitching (fasciculations) and cramping, which can lead to muscle discomfort, pain, or tiredness. Muscles in the leg are most commonly affected, although this condition may involve several parts of the body.
    