Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Myoclonic epilepsy with ragged red fibers ?
    ### Response:
    Myoclonic epilepsy with ragged red fibers (MERRF) is a multisystem disorder characterized by myoclonus, which is often the first symptom, followed by generalized epilepsy, ataxia, weakness, and dementia. Symptoms usually first appear in childhood or adolescence after normal early development.
    