Kleine Levin syndrome
is a rare disorder characterized by episodes of excessive sleep. Affected individuals may sleep for up to 20 hours per day during an episode. These episodes usually last for a few days to a few weeks. An episode may start abruptly and is sometimes associated with flu-like symptoms. During an episode, people with Kleine Levin syndrome can also display abnormal behavior, such as excessive food intake, irritability, childishness, disorientation, hallucinations, and an abnormally uninhibited sex drive. Affected individuals do not experience any of these features between episodes, and they may not be able to remember everything that happened during an episode. The time between episodes varies among individuals with this condition. Kleine Levin syndrome primarily affects adolescent males, but it also affects females. It may be caused by abnormal function of the hypothalamus and thalamus, parts of the brain that control appetite and sleep. Episodes usually decrease in frequency and intensity after about eight to 12 years. Source: Genetic and Rare Diseases Information Center (GARD), supported by ORDR-NCATS and NHGRI.