<unk>  (KLS) is a rare disorder characterized by persistent episodic hypersomnia and cognitive or mood changes. Many patients also experience hyperphagia, hypersexuality and other symptoms. Patients generally experience recurrent episodes of the condition for more than a decade and may return at a later age. Individual episodes generally last more than a week, sometimes lasting for months. The condition greatly affects the personal, professional, and social lives of sufferers. The severity of symptoms and the course of the<unk>  vary between sufferers. Patients commonly have about 20 episodes over about a decade. Several months generally elapse between episodes. The onset of the condition usually follows a viral infection; several different viruses have been observed to trigger KLS. It is generally only diagnosed after similar conditions have been excluded; MRI, CT scans, lumbar puncture, and toxicology tests are used to rule out other possibilities. The<unk> 's mechanism is not known, but the thalamus is thought to possibly play a role. SPECT has shown thalamic hypoperfusion of patients during episodes. KLS is very rare, occurring at a rate of 1 in 1 million, which limits research into genetic factors. The condition primarily affects adolescent males, though females can also be affected and the age of onset varies. There is no known cure, and there is little evidence supporting drug treatment. Lithium has been reported to have limited effects in case reports, decreasing the length of episodes and duration between them in some patients. Stimulants have been shown to promote wakefulness during episodes, but they do not counteract cognitive symptoms or decrease the duration of episodes. The condition is named after Willi<unk>  and Max<unk> , who described cases of the disease in the early 20th century. It was added to the International Classification of Sleep Disorders in 1990.
Kleine–Levin syndrome
Bulimia nervosa
Temple–Baraitser syndrome
Adams–Nance syndrome
Frey's syndrome
Urban–Rogers–Meyer syndrome
Wallis–Zieff–Goldblatt syndrome
Nance–Horan syndrome