Kleine-Levin Syndrome – Symptoms, Causes, Diagnosis, and Treatment

Sometimes referred to as Familial Hibernation Syndrome, Kleine-Levin Syndrome (KLS) is rare and it includes behavior changes (for example, increased sex drive), excessive amounts of sleep and excessive food intake. The condition mainly affects male teenage boys, and although these behaviors are all common in their age, symptoms in people suffering from KLS are extreme.

Sometimes referred to as Familial Hibernation Syndrome, Kleine-Levin Syndrome (KLS) is rare and it includes behavior changes (for example, increased sex drive), excessive amounts of sleep and excessive food intake. The condition mainly affects male teenage boys, and although these behaviors are all common in their age, symptoms in people suffering from KLS are extreme.

When awake, patients exhibit excessive daytime sleepiness; they might be lethargic, apathetic, disoriented, and can even have hallucinations. The symptoms show up in cycles, with periods of normal behavior in between. Cause of this disease is still unknown, and the weird thing about it is that the episodes become less frequent with age, and then they disappear entirely. They might reappear later in adulthood, but these cases are sporadic.

Scientists believe that genetic predispositions play a role in some cases, and some individuals are more prone to KLS because of that. Malfunctioning of the hypothalamus, a part of the brain that regulates sleep, appetite, body temperature, and many other things, is another suspect when it comes to the cause of KLS. Some experts think that it could be an autoimmune disease due to the high percentage of cases that exhibit signs of inflammation before the development of symptoms connected to KLS.


KLS is an extremely rare disorder characterized by the excessive need for prolonged periods of sleep (hypersomnia), excessive eating (hyperphagia), and abnormal behaviors. The onset of symptoms is very rapid, and they might persist between a few days and a few weeks. People with this condition might have 2 to 12 episodes each year, and they usually show no symptoms of the disease between the events. In most cases, the frequency of these episodes decreases with age and then suddenly disappears. However, there are reported cases of people experiencing these symptoms throughout late adulthood.

Individuals with KLS might sleep up to 20 hours a day, and they only wake up to eat and go to the bathroom. They can be awakened during the sleeping periods, but they are often overly tired, irritable and show the lack of emotions. They might also seem disoriented and confused and have difficulties speaking. In some cases, patients might experience vivid hallucinations where they feel detached from reality or have disconnected thinking.

Another big sign of KLS is an urge to overeat. Affected individuals don’t seem to feel hunger or even satisfaction and fullness after a meal. They simply consume all the available food no matter the type, condition or quality. Overeating combined with long periods of sleep and no activity can lead to weight gain. Unfortunately, obesity leads to several other health conditions such as high blood pressure, heart disease, diabetes, as well as sleep disorders such as sleep-related breathing disorders like obstructive sleep apnea.

Increased sex drive is also a symptom in some individuals. Others might experience behavioral abnormalities such as memory problems, lack of focus and motivation, and impaired concentration. Some patients were observed to show signs of aggression, anxiety, and depression. Hypersomnia affects all people with KLS, cognitive changes (96%), eating disturbances (80%), depressed mood (48%), hypersexuality (43%), and compulsions (29%).


KLS mostly affects adolescent males, and the symptoms usually start at the age of 15. However, there are reported cases of KLS affecting older males as well as females. While men are twice as more likely to develop KLS, women usually have longer disease course. Since it is a very rare disorder, it is hard to determine its precise frequency in the general population. Medical professionals even think because of the unknown cause of the disease, and its rarity, that the KLS is underdiagnosed, making it even harder to predict its prevalence.

The exact cause of KLS is still unknown, and scientists are working hard to figure this one out. It is speculated that the malfunction or damage to the hypothalamus might be the cause, as it is the part of the brain that helps regulate functions of appetite, sleep, thermoregulation, as well as many other things.  Since the flu-like symptoms and inflammation often show up before the signs of KLS, it led scientists to believe that the autoimmune process plays a role in the development of the condition. Autoimmune diseases happen when our body’s natural defense system that is protecting us against outside pathogens and diseases starts attacking our healthy tissues and organs.

Scientists have even proposed that KLS can be a result of head trauma or some other problem. In some sporadic cases, KLS has affected members of the same family, implicating that there might be genetic factors that may cause the development of this condition.

In a 2015 systematic review, researchers determined that infection or flu-like symptoms were present in more than two-thirds of cases, 3-5 days before the onset of KLS. Other triggers were more variable and rare, and they included heavy alcohol and marijuana consumption, head trauma, sleep deprivation, stress, mental exhaustion, menses, lactation, and other smaller factors. The disease symptoms lasted between 0.5 to 41 year, with an average duration of 8 years. Episodes lasted for ten days on average, with 3.5-month intervals in between. There were patients with secondary KLS, where the development of the condition was linked to prior stroke, post-traumatic brain hematoma, genetic and developmental diseases, multiple sclerosis, autoimmune encephalitis, or severe infectious encephalitis. Compared to patients with primary KLS, symptoms here appeared later on in life. The patients also experienced three times more episodes, with a longer duration of these events. The disease, however, didn’t last longer on average.


KLS robs the affected individuals of their time, energy, and health. When you are bed-driven, sleeping most of the time, and waking up just to fulfill your most basic needs, there is no room for anything else. People’s quality of life is severely reduced; they can’t go to school, work, or merely do some basic things that occupy our time. Episodes of KLS are terrible, and even though the symptoms are so severe, diagnosing the disease isn’t as easy as it seems. Experts need to rule out any other underlying causes, and the disorders that might show some similar symptoms like narcolepsy.

People with KLS are often diagnosed with a psychiatric disorder by mistake. Periods of hypersomnia, overeating, and withdrawal are all similar to severe clinical depression, and some people even experience periods of high energy after these episodes that mimic the manic events, so they can be misdiagnosed with a bipolar disorder. Narcolepsy, temporal lobe epilepsy, Kluver-Bucy syndrome, and multiple sclerosis can also produce similar symptoms, so doctors need to rule them out first.

And that is pretty much how the medical professionals diagnose KLS, they rule out every other possible disorder first, and then use the comprehensive medical history of a patient to determine if a person suffers from KLS. There are many medical professionals involved in this process, and they work together for quite some time to make the diagnosis of KLS. The description of symptoms and abnormal behaviors by the family is extremely helpful in setting the right diagnosis. Doctors will need to take several tests like EEG, MRI, cerebrospinal fluid and hormonal analysis.

Related Disorders

Narcolepsy is described by excessive sleepiness throughout the day, sudden muscle weakness, hallucination, sleep paralysis, and disrupted sleep during the night. People with narcolepsy also experience lack of energy, irresistible urge to fall asleep, and inability to stay awake during these “sleep attacks.” The symptoms of narcolepsy begin in the second decade of life, and the cause of this sleep disorder is unknown as well.

Many other sleep disorders show some similar symptoms and are causing disturbed sleep. These include cataplexy, sleep apnea, idiopathic hypersomnia, delayed sleep phase syndrome, and others. Depression and bipolar disorder are mostly mistaken with KLS because of the similar symptoms that the individuals go through. KLS can, in fact, lead to the development of depression since these episodes are very exhausting and might seem like there is just no way out. That’s why you should see your doctor if you notice any of the mentioned symptoms. They are trained to help you and can determine what is the underlying problem of your symptoms and sleep disruption.


After the clinical evaluation and diagnosis of Kleine-Levin Syndrome, there are different ways to combat the disease. There is no universal cure, and the treatment depends on the case, and is mostly aimed at battling individual symptoms. As with diagnosis, the treatment might also require a team of specialist. Pediatricians, psychologists, psychiatrists, neurologists, and other medical professionals need to work together to work out a plan for the treatment of adolescents with KLS.

Numerous medications have been used to treat the episodes of KLS so far, and none of them showed to be a good effective solution. Amphetamines are mostly used to treat sleepiness symptoms, but they are not useful in eliminating cognition impairment and other abnormal behaviors. Lithium was successful in improving strange behavior and the recovery of symptoms. The effectiveness of lithium was maybe because of the similarity of KLS with bipolar disorder, but whatever it is, the important thing is that the duration of the episodes was significantly shorter. Carbamazepine had similar effects in few cases. Different medications have shown no significant improvement, while some even worsened the condition. During the time in between the episodes, only lithium showed beneficial in delaying the relapses of the events. The affected individuals shouldn’t be left to wander around unattended, shouldn’t drive a car, or operate heavy machinery. The family of the patient should learn to recognize the symptoms of the upcoming episode in the very beginning and minimize the damage it might produce. The development of depression and anxiety should also be closely monitored and treated if needed. It is essential to maintain proper sleep hygiene between the episodes, keep a sleep-wake schedule, avoid alcohol, and contact with sick people.

The disease usually shows up during the adolescence and lasts, up until the beginning or mid-20s, and then resolves it on its own. Because of this and the ineffectiveness of various approaches, some medical professionals might suggest no medical treatment. Instead, they might suggest informing yourself, connecting to the other families affected by this condition, and trying to improve all aspects of like, so that the disease passes as quickly as possible. The parents of affected adolescents should create a safe and relaxing environment, and all the school and other obligations should be postponed or adjusted until the symptoms disappear.

Scientists are saying that we need to investigate further the genetic component and treatment options for KLS. They are suggesting that we might need immunosuppressants and antivirals as the onset of the disease could be due to infection and autoimmune problems. One thing is sure, KLS requires a lot more research and understanding, but it is hard to do so since the condition is infrequent.


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