What Is Kleine-Levin Syndrome?

Kleine-Levin Syndrome or KLS is an extremely rare and complex neurological disorder characterized by recurrent periods of excessive amounts of sleep, altered behavior, and disorientation. Episodes occur approximately two to 12 times per year and usually last for a few days to a few weeks, during which time all normal daily activities stop. During an episode, people with KLS are not able to care for themselves, attend school or work and most are uncommunicative or have difficulties speaking such as slurred speech even when awake. The time between episodes varies and during these times, those with KLS appear to be in perfect health with no evidence of behavioral or physical dysfunction. KLS episodes may continue for 10 years or more. In some cases, symptoms subside with advancing age, most often by early adult life. However, in other cases, the disorder persists throughout adulthood.

The disorder primarily strikes adolescent males (approximately 70%) but can occur in younger children and adults both male and female. Prevalence is slightly higher in the Ashkenazi Jewish population. The exact cause of Kleine-Levin Syndrome is unknown. It is speculated that symptoms may develop due to malfunction or damage to the portion of the brain that helps to regulate functions such as sleep, appetite, and body temperature (hypothalamus). As with most diseases with no known cause, some researchers have speculated that, in some cases, symptoms may develop as a result of a head injury or an infectious disease affecting the hypothalamus; however, this is unproven. The association of an infection before onset, a young age at onset, a recurrence of symptoms and possible genetic predisposition is suggestive of an autoimmune disease. At this time there is no effective treatment or cure.


Kleine-Levin Syndrome Foundation – What is KLS?

NORD National Organization for Rare Disorders

NIH GARD National Institutes of Health – Genetic and Rare Diseases Information Center

NIH NINDS National Institutes of Health – National Institute of Neurological Disorders and Stroke

Aurelie Kas, Sophie Lavault, Marie-Odile Habert, Isabelle Arnulf; Feeling unreal: a functional imaging study in patients with Kleine-Levin syndrome. Brain 2014; 137 (7): 2077-2087.


Miglis, M. G., & Guilleminault, C. (2014). Kleine-Levin syndrome: a review. Nature and Science of Sleep, 6, 19–26.