Kleine-Levin Syndrome: A Mysterious and Rare Sleep Disorder

Kleine-Levin Syndrome is a rare disorder where intermittent episodes of extreme fatigue and cognitive disturbances mysteriously appear, and years later, fade away.

By Nicole Gleichmann

Imagine a scenario where your sleep habits, cognitive function, and animal instincts one day veer from completely normal to extremely unusual for no apparent reason. This is what happens for those who develop Kleine-Levin Syndrome, a condition that seemingly comes from nowhere, and just as mysteriously, disappears.

Affecting less than 200,000 people in the United State, this is one of many rare diseases for which there are more questions than answers. Read on to learn about Kleine-Levin Syndrome: what we know, what we don’t know, and what you should do if you or a family member develops symptoms.

What is Kleine-Levin Syndrome?

Kleine-Levin Syndrome (KLS) is a neurological and sleep disorder that’s most common amongst adolescent males (around 70% of those with this condition are male). It’s characterized by recurring periods of excessive sleepiness and cognitive troubles that come and go over the course of many years.

There are many other possible symptoms, although the exact symptoms vary from one patient to another. One of the most interesting aspects of this disease is that it nearly always tapers off with age. While most people will experience a full recovery in around 4-8 years, there are some people who fall outside of this range.

In a review that looked at 110 patients with primary KLS, the shortest disease frequency was 6 months, and the longest was 41 years. Rarely, people who think that their KLS has completely resolved can experience a sporadic episode later in life.

Thanks to the unpredictability of this condition, it’s particularly difficult for those affected to maintain a high quality of life. It nearly always interferes with work and school and can be a burden on family, friends, and other caretakers.

Symptoms of Kleine-Levin Syndrome

There is no one set of symptoms that applies to all affected individuals. The most common symptom is the need for excessive sleep, totaling up to 20 hours per day. A lack of sexual impulse control and compulsive eating are two of the other common symptoms.

Other symptoms include:

  • Behavioral disturbances: Irritability, childishness, apathy, and other behavioral abnormalities.
  • Hallucinations and confusion: Patients often experience periods of confusion or full-on hallucinations. They might describe episodes as hazy or confusing.
  • Cognitive abnormalities: Difficulties with speech, memory, learning, and focus can occur.
  • Mood troubles: Some patients show signs of depression during episodes and appear manically happy for a short period following recovery.
  • Compulsive behavior: Compulsive singing, writing, body rocking, pacing, and other behaviors have been noted.
  • Hypersensitivity: Patients may be overly sensitive to light and sound.

Symptoms come on unexpectedly and typically last anywhere from a few days to a few weeks. These periods are often referred to as “episodes.” In between episodes, patient’s will return to their normal selves, with sleep, behavior, and cognition normalizing. This healthy period can range from weeks to months.

While some people will remember what happens during their episodes, others will suffer from partial amnesia, not clearly remembering what they said or did.

KLS episodes tend to become less frequent, intense, and long as one nears the end of the disease. Eventually, the disorder will spontaneously disappear, allowing those affected to return to living a normal life.

The Potential Dangers of KLS

The biggest danger that KLS poses is to the overall quality of life of those affected. Children often miss big chunks of school and adults can have difficulties maintaining jobs and relationships.

While most episodes are marked by being bedridden and lethargic, some people can experience more intense episodes when it comes to behavior. There are rare examples of KLS episodes where the symptoms became severe enough to pose a danger to those around the patient.

Furthermore, there have been some cases where long-term cognitive deficits have been noted. It’s not known if these instances were a direct consequence of KLS and its impact on the brain, or if it was due to the interruption of day-to-day life. For example, kids missing lots of school might develop learning difficulties.

Are There Clues That an Episode is Coming?

If you or a loved one has been diagnosed with Kleine-Levin Syndrome, it’s only natural to try and find some patterns that might help you predict when an episode is around the corner. Being able to predict these periods can be helpful for planning around work, school, or other activities.

While most people won’t have any noticeable triggering events, nearly 9% of patients experience an infection or fever before recurrent episodes.

Keep a journal of your day-to-day life, including how much you sleep, what you eat and drink, drugs you take, sicknesses that you have, and anything else that you feel might correlate to an episode. Most people will not find a definitive pattern, but there are some who might be able to partially predict episodes.

Who is at Risk?

While most affected individuals display their first symptoms in their teen years, adolescents are not the only ones at risk. In a systematic review of published articles on KLS patients, researchers found that:

  • The median age of onset was 15 years old
  • There was a 2:1 ratio of men to women affected
  • The ages of those affected ranged from 4 to 82 years old
  • Israel had the highest prevalence, although it was found in many countries throughout the world
  • 6 patients experienced disease onset at 35 years or older

On average, women experience a longer duration of this disease when compared with men, despite other factors being similar. These include the age of onset and episode frequency, duration, and symptom severity.

Additionally, the studies and articles published suggest that KLS might be more prevalent in the Jewish population. It isn’t known whether this pattern is thanks to an increased risk in the Jewish community or to a reporting bias. For instance, it’s possible that more articles have been published in Israel due to a factor other than higher disease frequency, such as a local expert who is dedicated to doing KLS research.

There is even evidence of this condition having a genetic component, such as multiple families experiencing more than one person with KLS. More research is needed to determine if there is, indeed, a hereditary component.

What Causes Kleine-Levin Syndrome?

Researchers are still on the hunt for the cause of this bizarre disease. It’s believed that the symptoms may be due to something going awry in the regions of the brain responsible for sleep patterns and appetite, the hypothalamus and the thalamus.

There is evidence that KLS onset may be caused by an infection or another occurrence that happens directly prior to the initial episode. In the systematic review discussed earlier, researchers found that over 2/3 of patients experienced an infection or fever immediately prior to initial onset. This high incidence makes it likely that a pathogen is involved in KLS pathogenesis.

Unfortunately, the research thus far has not discovered a pathogen responsible for KLS. For those who did experience an illness or infection prior to the start of the disease, the pathogens responsible for the illnesses were not the same. This led researchers to conclude that KLS might be caused by an unknown disease agent, or that certain infections might uncover a previously existing disease.

Diagnosing KLS

There is no test for KLS. Most people with KLS leave the doctor with test results that would indicate a clean bill of health.

Researchers have searched for telltale signs of the disease. This includes testing for brain lesions, cerebrospinal fluid abnormalities, brain imaging, and more. Unfortunately, none of these tests have found a KLS marker.

If you believe that you or one of your family members has developed KLS, visit your primary care physician. They will likely refer you to a specialist to rule out other conditions. If your tests do not reveal any other condition and you exhibit the typical symptoms of KLS, you will likely be given a KLS diagnosis.

Treatment for Kleine-Levin Syndrome

As it stands presently, researchers and doctors have had little luck using drugs to treat KLS. The two medications that may help some patients are amphetamines and lithium.

Be sure to consult with your doctor before taking medications. 


Amphetamines are central nervous system stimulants used for conditions as varied as attention-deficit-hyperactive disorder (ADHD) and sleep disorders. They can provide stimulation that leads to increased alertness and decreased fatigue.

While amphetamines were found to help some KLS patients with their hypersomnia, it, unfortunately, did not help with the other symptoms. This means that the patients could feel more awake, but the cognitive and behavioral deficits were still there. In some patients, this made other symptoms harder to manage.


Lithium, on the other hand, may have helped to prevent relapses in some patients. With 29 cases of KLS patients treated with lithium, many did experience less frequent episodes. Unfortunately, lithium has some serious side effects and is difficult to take.

Other Treatments

Multiple other treatments have been attempted by doctors, including mood stabilizers, antidepressant drugs, and antiepileptic drugs. Sadly, when comparing these drugs to no treatment, there appears to be no benefit.

The difficulty with testing drugs for those with KLS is that the duration of the disease is so variable and unpredictable. Thus far there have not been any placebo-controlled studies examining treatments. Hopefully, there will be clinical trials in the future examining the effect of other drugs, like antiviral agents, in a placebo-controlled trial.

Learning to Live with KLS

Because there is no effective drug treatment, it’s recommended that those with KLS learn strategies to cope with the disorder. Some general tips include:

  • Educating those around you: Be open with your family, friends, school, and workplace about your condition. Set reasonable expectations so that you can get back to your regular life quickly once your symptoms cease.
  • Find a support group: There are support groups for those with KLS. Joining online or in-person support groups can be a great place to find people that relate. You might learn of new ways to help manage the condition or find a workplace that’s understanding.
  • Create a plan: Work with those close to you to come up with a step-by-step plan for when you experience an episode.
  • Keep the future in mind: Most people who are diagnosed with KLS will get better without treatment in a matter of years. Remind yourself that your condition is likely to get better. This can help you and your family stay optimistic during the tough times.

Final Thoughts

Living with Kleine-Levin Syndrome can be extremely difficult for patients and those close to them. The best course of action is learning to manage KLS and wait it out. For most, this disease will disappear as mysteriously as it appeared.

Comments (0)