Kleine-Levin syndrome (KLS) is a rare disorder that causes recurring periods of excessive sleepiness. In some cases, this means up to 20 hours a day are spent sleeping. For this reason, the condition is commonly referred to as “sleeping beauty syndrome.”

KLS can also produce confusion and changes in behavior. This disorder can affect anyone, but teenage boys develop the condition more often than any other group. About 70 percent of people with this disorder are male.

Episodes can come and go over an extended period — sometimes for as long as 10 years. During each episode, it can be difficult to attend school or work, or participate in other activities.

People living with KLS may not experience symptoms every day. In fact, people with the condition typically don't have any symptoms between episodes. When symptoms do appear, they can last a few days, weeks, or even months.

Common symptoms include extreme sleepiness. There may be a strong desire to go to bed and trouble getting up in the morning.

During an episode, it's not uncommon to sleep up to 20 hours per day. People living with KLS may get up to use the bathroom and eat, then go back to sleep.

Fatigue can be so severe that people with KLS are bedridden until an episode passes. This takes time and energy away from family, friends, and personal obligations.

Episodes can also trigger other symptoms, such as:

This may result from reduced blood flow to parts of the brain during an episode.

KLS is an unpredictable condition. Episodes can recur suddenly and without warning weeks, months, or years later.

Most people resume normal activity after an episode without any behavioral or physical dysfunction. However, they may have little memory of what happened during an episode.

The exact cause of KLS is unknown, but some doctors believe certain factors can increase your risk for this condition.

For example, KLS may arise from an injury in the hypothalamus, the part of the brain that controls sleep, appetite, and body temperature. A possible injury could be falling and hitting your head, although more research is needed to confirm this link.

Some people develop KLS after an infection like the flu. This has led some researchers to believe KLS may be a type of autoimmune disorder. An autoimmune disease is when the body’s immune system attacks its own healthy tissue.

Some incidents of KLS may also be genetic. There are cases where the disorder affects more than one person in a family. However, no clear genetic associations have been found in population studies to date, and further research is needed.

KLS is a difficult disorder to diagnose. Some people are misdiagnosed with a psychiatric disorder because KLS can occur with other psychiatric symptoms. As a result, it can take an average of four years for someone to receive an accurate diagnosis.

Understandably, you and your family want quick answers. However, a KLS diagnosis is a process of exclusion. There isn’t a single test to help your doctor confirm this condition. Instead, your doctor may conduct a series of tests to rule out other possible illnesses.

Symptoms of KLS can mimic other health conditions. Your doctor may conduct a physical examination and diagnostic testing. These may include blood work, a sleep study, or imaging tests such as a CT scan or MRI of your head.

Your doctor uses these tests to check for, and rule out, the following conditions:

Excessive sleepiness is also a symptom of depression. Your doctor may suggest a mental health evaluation. This helps your doctor assess whether symptoms are due to severe depression or another mood disorder. Learn more about sleep disorders in children.

Several medications are available to help you manage symptoms. Taking medication may help reduce the length of an episode and prevent future episodes.

Stimulant pills are an option for treating KLS. These medications promote wakefulness and are effective at reducing sleepiness, but they can cause irritability. Options like methylphenidate (Concerta) and modafinil (Provigil) may help to reduce sleepiness.

Medications that treat mood disorders may also be beneficial. For example, lithium (Lithane) and carbamazepine (Tegretol) — which are commonly used to treat bipolar disorder — may relieve symptoms of KLS.

More recently, there are reports of people responding to clarithromycin (an antibiotic and GABA antagonist). However, there is currently not enough evidence to know how well medications work on KLS. There is a lack of clinical trials that rigorously compare drug efficacy.

Because episodes of KLS can occur over a span of 10 years or more, living with this condition can have a tremendous impact on your life. It can interfere with your ability to work, go to school, and cultivate relationships with friends and family.

It can also trigger anxiety and depression, primarily because you don't know when an episode will occur or how long it will last.

If you experience increased hunger and overeat during episodes, you may be more likely to gain weight.

Talk to your doctor about how to identify an approaching episode. Tiredness and sleepiness caused by KLS can occur suddenly. You could injure yourself or others if an episode occurs while you are operating a motor vehicle or machinery. You may be able to remove yourself from a potentially dangerous situation if you learn how to identify an impending episode. Learn more about sleep disorders in older adults.

Your outlook depends on the severity of your symptoms. Symptoms generally decrease with each year. Episodes become more mild and infrequent.

Although KLS symptoms can come and go over the course of many years, it’s possible for your symptoms to disappear one day and never return. People with KLS are typically considered “cured” when they haven’t had an episode for six or more years.

Also, check out the best sleep disorder blogs of the year here.