Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Kleine-Levin Syndrome ?
    ### Response:
    Kleine-Levin syndrome is a rare disorder that primarily affects adolescent males (approximately 70 percent of those with Kleine-Levin syndrome are male). It is characterized by recurring but reversible periods of excessive sleep (up to 20 hours per day). Symptoms occur as "episodes," typically lasting a few days to a few weeks.
    