ABOUT KLEINE-LEVIN SYNDROME
Kleine-Levin syndrome (KLS) is a rare disorder in which affected people experience episodes at least once per year during which they sleep for at least 11 hours out of every day (but often for days at a time), eat excessively (megaphagia), have abnormal thinking and behavior, and hypersexuality. Between episodes, their alertness, behavior, and thinking are normal.
Both the International Classification of Sleep Disorders and the Diagnostic and Statistical Manual of Mental Disorders include criteria to diagnose KLS, but there are no biomarkers—no substances in the body that can be measured—that can help doctors in making the diagnosis of KLS. Some scientists who study KLS think that KLS is caused by something in the immune system that makes the part of the brain called the hypothalamus not work properly. Nerve cells (neurons) in the hypothalamus produce two neurotransmitters, hypocretin and histamine, that are involved in regulating alertness, feeding, and neuroendocrine and autonomic function.