The Kleine-Levin hibernation syndrome (KLS) is a rare autosomal dominant disorder characterized by episodes of behavior and cognitive disturbance, and hypersomnia.  The condition may also be associated with episodes of increased feeding, hypersexuality, and/or mood disorders and depression.  These episodes may occur from 2 to 12 times every year, with each episode lasting for a few days, or sometimes even up to a month.  Hypersexuality is more commonly seen in male patients, while mood disorders are more frequent in females.  On the whole, the condition affects more males than females, and age of onset is usually around 15 years. 

KLS is an extremely rare disease, affecting one in a million people worldwide.  Diagnosis can be made through EEG and brain scintigraphy in addition to a detailed medical history.  Since the symptoms of the condition mimic those of severe depression, and each episode may be followed by short periods of high energy, patients may be incorrectly diagnosed with bipolar disorder.  Treatment is supportive. 

KLS is not typically an inherited condition.  However, in a small percentage of cases, familial clustering has been noted.  In addition, the fact that the Jewish population is more susceptible to the condition has also suggested a genetic component to the syndrome.  In the familial cases, KLS has been shown to follow an autosomal dominant pattern of inheritance.  An association of KLS with HLA-DQ2 has been described in some studies.  However, there is no known gene to cause KLS. Some familial studies have also indicated autosomal recessive inheritance.