Narcolepsy is a chronic sleep disorder that disrupts the normal sleep-wake cycle. Although this condition can appear at any age, it most often begins in adolescence.

Narcolepsy is characterized by excessive daytime sleepiness. Affected individuals feel tired during the day, and several times a day they may experience an overwhelming urge to sleep. "Sleep attacks" can occur at unusual times, such as during a meal or in the middle of a conversation. They last from a few seconds to a few minutes and often lead to a longer nap, after which affected individuals wake up feeling refreshed.

Another common feature of narcolepsy is cataplexy, which is a sudden loss of muscle tone in response to strong emotion (such as laughing, surprise, or anger). These episodes of muscle weakness can cause an affected person to slump over or fall, which occasionally leads to injury. Episodes of cataplexy usually last just a few seconds, and they may occur from several times a day to a few times a year. Most people diagnosed with narcolepsy also have cataplexy. However, some do not, which has led researchers to distinguish two major forms of the condition: narcolepsy with cataplexy and narcolepsy without cataplexy.

Narcolepsy also affects nighttime sleep. Most affected individuals have trouble sleeping for more than a few hours at night. They often experience vivid hallucinations while falling asleep (hypnogogic hallucinations) or while waking up (hypnopompic hallucinations). Affected individuals often have realistic and distressing dreams, and they may act out their dreams by moving excessively or talking in their sleep. Many people with narcolepsy also experience sleep paralysis, which is an inability to move or speak for a short period while falling asleep or awakening. The combination of hallucinations, vivid dreams, and sleep paralysis is often frightening and unpleasant for affected individuals.

Some people with narcolepsy have all of the major features of the disorder, while others have only one or two. Most of the signs and symptoms persist throughout life, although episodes of cataplexy may become less frequent with age and treatment.

Narcolepsy is a chronic neurological disorder that affects the brain's ability to control sleep-wake cycles. People with narcolepsy may feel rested after waking, but then feel very sleepy throughout much of the day. Many individuals with narcolepsy also experience uneven and interrupted sleep that can involve waking up frequently during the night.

Narcolepsy can greatly affect daily activities. People may unwillingly fall asleep even if they are in the middle of an activity like driving, eating, or talking. Other symptoms may include sudden muscle weakness while awake that makes a person go limp or unable to move (cataplexy), vivid dream-like images or hallucinations, and total paralysis just before falling asleep or just after waking up (sleep paralysis).

In a normal sleep cycle, a person enters rapid eye movement (REM) sleep after about 60 to 90 minutes. Dreams occur during REM sleep, and the brain keeps muscles limp during this sleep stage, which prevents people from acting out their dreams. People with narcolepsy frequently enter REM sleep rapidly, within 15 minutes of falling asleep. Also, the muscle weakness or dream activity of REM sleep can occur during wakefulness or be absent during sleep. This helps explain some symptoms of narcolepsy.

If left undiagnosed or untreated, narcolepsy can interfere with psychological, social, and cognitive function and development and can inhibit academic, work, and social activities.

There are two major types of narcolepsy:

1. Type 1 narcolepsy (previously known as narcolepsy with cataplexy)—This diagnosis is based on the individual either having low levels of a brain hormone (hypocretin) or reporting cataplexy and having excessive daytime sleepiness on a special nap test.
2. Type 2 narcolepsy (previously known as narcolepsy without cataplexy)—People with this condition experience excessive daytime sleepiness but usually do not have muscle weakness triggered by emotions. They usually also have less severe symptoms and have normal levels of the brain hormone hypocretin.

A condition known as secondary narcolepsy can result from an injury to the hypothalamus, a region deep in the brain that helps regulate sleep. In addition to experiencing the typical symptoms of narcolepsy, individuals may also have severe neurological problems and sleep for long periods (more than 10 hours) each night.

Narcolepsy affects about 1 in 2,000 people in the United States and Western Europe. However, the disorder is likely underdiagnosed, particularly in people with mild symptoms. Worldwide, narcolepsy appears to be most common in Japan, where it affects an estimated 1 in 600 people.

Narcolepsy affects both males and females equally. Symptoms often start in childhood, adolescence, or young adulthood (ages 7 to 25), but can occur at any time in life. Since people with narcolepsy are often misdiagnosed with other conditions, such as psychiatric disorders or emotional problems, it can take years for someone to get the proper diagnosis.

Narcolepsy may have several causes. Nearly all people with narcolepsy who have cataplexy have extremely low levels of the naturally occurring chemical hypocretin, which promotes wakefulness and regulates REM sleep. Hypocretin levels are usually normal in people who have narcolepsy without cataplexy.

Although the cause of narcolepsy is not completely understood, current research suggests that narcolepsy may be the result of a combination of factors working together to cause a lack of hypocretin. These factors include:

• Autoimmune disorders—When cataplexy is present, the cause is most often the loss of brain cells that produce hypocretin. Although the reason for this cell loss is unknown, it appears to be linked to abnormalities in the immune system. Autoimmune disorders occur when the body's immune system turns against itself and mistakenly attacks healthy cells or tissue. Researchers believe that in individuals with narcolepsy, the body's immune system selectively attacks the hypocretin-containing brain cells because of a combination of genetic and environmental factors.
• Family history—Most cases of narcolepsy are sporadic, meaning the disorder occurs in individuals with no known family history. However, clusters in families sometimes occur—up to 10 percent of individuals diagnosed with narcolepsy with cataplexy report having a close relative with similar symptoms.
• Brain injuries—Rarely, narcolepsy results from traumatic injury to parts of the brain that regulate wakefulness and REM sleep or from tumors and other diseases in the same regions.

In the past few decades, scientists have made considerable progress in understanding narcolepsy and identifying genes strongly associated with the disorder. Groups of neurons in several parts of the brain interact to control sleep, and the activity of these neurons is controlled by a large number of genes. The loss of hypocretin-producing neurons in the hypothalamus is the primary cause of type 1 narcolepsy. These neurons are important for stabilizing sleep and wake states.

The human leukocyte antigen (HLA) system of genes plays an important role in regulating the immune system. This gene family provides instructions for making a group of related proteins called the HLA complex, which helps the immune system distinguish between good proteins from an individual's own body and bad ones made by foreign invaders like viruses and bacteria.

One of the genes in this family is HLA-DQB1. A variation in this gene, called HLA-DQB1*06:02, increases the chance of developing narcolepsy, particularly the type of narcolepsy with cataplexy and a loss of hypocretins (also known as orexins). HLA-DQB1*06:02 and other HLA gene variations may increase susceptibility to an immune attack on hypocretin neurons, causing these cells to die. Most people with narcolepsy have this gene variation and may also have specific versions of closely related HLA genes.

However, it is important to note that these gene variations are common in the general population and only a small portion of the people with the HLA-DQB1*06:02 variation will develop narcolepsy. This indicates that other genetic and environmental factors are important in determining if an individual will develop the disorder.

Narcolepsy follows a seasonal pattern and is more likely to develop in the spring and early summer after the winter season, a time when people are more likely to get sick. By studying people soon after they develop the disorder, scientists have discovered that individuals with narcolepsy have high levels of anti-streptolysin O antibodies, indicating an immune response to a recent bacterial infection such as strep throat. Also, the H1N1 influenza epidemic in 2009 resulted in a large increase in the number of new cases of narcolepsy. Together, this suggests that individuals with the HLA-DQB1*06:02 variation are at risk for developing narcolepsy after they are exposed to a specific trigger, like certain infections that trick the immune system to attack the body.

Normal Function

The HLA-DQA1 gene provides instructions for making a protein that plays a critical role in the immune system. The HLA-DQA1 gene is part of a family of genes called the human leukocyte antigen (HLA) complex. The HLA complex helps the immune system distinguish the body's own proteins from proteins made by foreign invaders such as viruses and bacteria.

The HLA complex is the human version of the major histocompatibility complex (MHC), a gene family that occurs in many species. The HLA-DQA1 gene belongs to a group of MHC genes called MHC class II. MHC class II genes provide instructions for making proteins that are present on the surface of certain immune system cells. These proteins attach to protein fragments (peptides) outside the cell. MHC class II proteins display these peptides to the immune system. If the immune system recognizes the peptides as foreign (such as viral or bacterial peptides), it triggers a response to attack the invading viruses or bacteria.

The protein produced from the HLA-DQA1 gene attaches (binds) to the protein produced from another MHC class II gene, HLA-DQB1. Together, they form a functional protein complex called an antigen-binding DQαβ heterodimer. This complex displays foreign peptides to the immune system to trigger the body's immune response.

Each MHC class II gene has many possible variations, allowing the immune system to react to a wide range of foreign invaders. Researchers have identified hundreds of different versions (alleles) of the HLA-DQA1 gene, each of which is given a particular number (such as HLA-DQA1*05:01).

Health Conditions Related to Genetic Changes

Celiac disease

At least two specific combinations of HLA gene variants (HLA haplotypes) have been found to increase the risk of developing celiac disease, a disorder in which inflammation damages the intestinal tract and other organs and tissues. One of these haplotypes, known as DQ2, is composed of the protein produced from HLA-DQA1 gene variants known as HLA-DQA1*05:01 or HLA-DQA1*05:05 bound to the protein produced from HLA-DQB1 gene variants known as HLA-DQB1*02:01 or HLA-DQB1*02:02. The other haplotype, known as DQ8, is composed of the protein produced from HLA-DQA1 gene variants known as HLA-DQA1*03:01 or HLA-DQA1*03:02 bound to the protein produced from the HLA-DQB1 gene variant known as HLA-DQB1*03:02.

The DQ2 and DQ8 haplotypes, which may occur separately or together, seem to increase the risk of an inappropriate immune response to the protein gluten, which is found in wheat, rye, and barley. This immune system malfunction results in the damage to the body's organs and tissues that occurs in celiac disease. However, the DQ2 and DQ8 haplotypes are also found in 30 percent of the general population, and only 3 percent of individuals with these haplotypes develop celiac disease.

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Type 1 diabetes

Combinations of variations in the HLA-DQA1 gene and other HLA genes affect the risk of type 1 diabetes. Type 1 diabetes is characterized by high blood sugar (glucose) levels resulting from a shortage of the hormone insulin and is caused by autoimmune damage to insulin-producing cells in the pancreas.

Type 1 diabetes risk is most increased by two HLA haplotypes involving variations of the HLA-DQA1 and HLA-DQB1 genes and another HLA gene called HLA-DRB1. One haplotype, written as DRB1*03:01-DQA1*05:01-DQB1*02, is called DR3. The other haplotype, written as DRB1*04:01/02/04/05/08-DQA1*03:01-DQB1*02, is called DR4. People at highest risk of developing type 1 diabetes have one copy of the DR3 haplotype and one copy of the DR4 haplotype in each cell. Other HLA haplotypes only mildly increase the risk of type 1 diabetes, while some haplotypes seem to protect against developing this condition. Variations in other genes and environmental factors are also thought to affect the risk of this complex disorder.

Autoimmune disorders

Certain normal variations of the HLA-DQA1 gene have been associated with increased risk of autoimmune disorders, which occur when the immune system malfunctions and attacks the body's own tissues and organs. It is unclear how different versions of the HLA-DQA1 gene influence the risk of developing autoimmune disorders. These conditions are thought to result from a combination of multiple environmental and genetic factors. Changes in other HLA and non-HLA genes, some of which remain unknown, also likely contribute to the risk of developing these complex conditions.

Other disorders

Normal variations in the HLA-DQA1 gene can affect the body's ability to recognize and react to foreign invaders (pathogens). For example, variations of this gene have been shown to increase or decrease a person's chance of getting infections such as hepatitis B and leprosy or may affect the severity of illness if infection occurs.

A particular variant of the HLA-DQA1 gene known as HLA-DQA1*02:01 increases the risk of liver damage in women with advanced breast cancer treated with a drug called lapatinib. Researchers suggest that the variant may increase immune system sensitivity to the drug, resulting in inflammation that damages the liver.

Other Names for This Gene

• DC-1 alpha chain
• DC-alpha
• DQ-A1
• FLJ27088
• FLJ27328
• GSE
• HLA class II histocompatibility antigen, DQ alpha 1 chain
• HLA class II histocompatibility antigen, DQ alpha 1 chain precursor
• HLA class II histocompatibility antigen, DQ(W3) alpha chain
• HLA-DCA
• HLA-DQA
• leucocyte antigen DQA1
• leukocyte antigen alpha chain
• MGC149527
• MHC class II antigen
• MHC class II DQA1
• MHC class II HLA-D alpha glycoprotein
• MHC class II HLA-DQ-alpha-1
• MHC class II surface glycoprotein
• MHC HLA-DQ alpha

Genomic Location

Normal Function

The HLA-DQB1 gene provides instructions for making a protein that plays a critical role in the immune system. The HLA-DQB1 gene is part of a family of genes called the human leukocyte antigen (HLA) complex. The HLA complex helps the immune system distinguish the body's own proteins from proteins made by foreign invaders such as viruses and bacteria.

The HLA complex is the human version of the major histocompatibility complex (MHC), a gene family that occurs in many species. The HLA-DQB1 gene belongs to a group of MHC genes called MHC class II. MHC class II genes provide instructions for making proteins that are present on the surface of certain immune system cells. These proteins attach to protein fragments (peptides) outside the cell. MHC class II proteins display these peptides to the immune system. If the immune system recognizes the peptides as foreign (such as viral or bacterial peptides), it triggers a response to attack the invading viruses or bacteria.

The protein produced from the HLA-DQB1 gene attaches (binds) to the protein produced from another MHC class II gene, HLA-DQA1. Together, they form a functional protein complex called an antigen-binding DQαβ heterodimer. This complex displays foreign peptides to the immune system to trigger the body's immune response.

Each MHC class II gene has many possible variations, allowing the immune system to react to a wide range of foreign invaders. Researchers have identified hundreds of different versions (alleles) of the HLA-DQB1 gene, each of which is given a particular number (such as HLA-DQB1*06:02).

Health Conditions Related to Genetic Changes

Celiac disease

At least two specific combinations of HLA gene variants (HLA haplotypes) have been found to increase the risk of developing celiac disease, a disorder in which inflammation damages the intestinal tract and other organs and tissues. One of these haplotypes, known as DQ2, is composed of the protein produced from HLA-DQB1 gene variants known as HLA-DQB1*02:01 or HLA-DQB1*02:02 bound to the protein produced from HLA-DQA1 gene variants known as HLA-DQA1*05:01 or HLA-DQA1*05:05. The other haplotype, known as DQ8, is composed of the protein produced from the HLA-DQB1 gene variant known as HLA-DQB1*03:02 bound to the protein produced from HLA-DQA1 gene variants known as HLA-DQA1*03:01 or HLA-DQA1*03:02.

The DQ2 and DQ8 haplotypes, which may occur separately or together, seem to increase the risk of an inappropriate immune response to the protein gluten, which is found in wheat, rye, and barley. This immune system malfunction results in the damage to the body's organs and tissues that occurs in celiac disease. However, the DQ2 and DQ8 haplotypes are also found in 30 percent of the general population, and only 3 percent of individuals with the gene variants develop celiac disease.

Narcolepsy

A version of the HLA-DQB1 gene called HLA-DQB1*06:02 increases the risk of developing the sleep disorder narcolepsy, particularly in people who also have cataplexy. (Cataplexy is a sudden loss of muscle tone in response to strong emotion, such as laughing, surprise, or anger.) It is unclear how HLA-DQB1*06:02 causes this elevated risk. However, there is increasing evidence that narcolepsy is related to a malfunction of the immune system.

The sleep abnormalities associated with narcolepsy likely result from a loss of particular brain cells (neurons) in a part of the brain called the hypothalamus. These cells normally produce chemicals called hypocretins (also known as orexins), which have many important functions in the body. In particular, hypocretins regulate the daily sleep-wake cycle. Researchers speculate that an abnormality of the immune system may trigger the loss of hypocretin-producing neurons in people with narcolepsy. However, there is no direct evidence to show that immune system factors are responsible for this loss.

Most people who have narcolepsy with cataplexy have the HLA-DQB1*06:02 variation, and many also have specific versions of other, closely related HLA genes (including HLA-DQA1). However, these variations are very common in the general population, and only a small percentage of people with particular variations in HLA genes develop narcolepsy. Other genetic and environmental factors, for example certain bacterial and viral infections, also affect the chances of developing this disorder.

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Type 1 diabetes

Combinations of variations in the HLA-DQB1 gene and other HLA genes affect the risk of type 1 diabetes. Type 1 diabetes is characterized by high levels of blood glucose, also called blood sugar, resulting from a shortage of the hormone insulin and is caused by autoimmune damage to insulin-producing cells in the pancreas.

Type 1 diabetes risk is most increased by two specific combinations of variations of the HLA-DQB1 and HLA-DQA1 genes and another HLA gene called HLA-DRB1. One haplotype, written as DRB1*03:01-DQA1*05:01-DQB1*02, is called DR3. The other haplotype, written as DRB1*04:01/02/04/05/08-DQA1*03:01-DQB1*02, is called DR4. People at highest risk of developing type 1 diabetes have one copy of the DR3 haplotype and one copy of the DR4 haplotype in each cell. Other HLA haplotypes only mildly increase the risk of type 1 diabetes, while some haplotypes seem to protect against developing this condition. Variations in other genes and environmental factors are also thought to affect the risk of this complex disorder.

Autoimmune disorders

Normal variations of the HLA-DQB1 gene have been associated with several additional disorders. Most of these disorders have an autoimmune basis, which means they occur when the immune system malfunctions and attacks the body's own tissues and organs. Autoimmune disorders that have been associated with HLA-DQB1 include multiple sclerosis, pemphigus, and type 1 diabetes (described below).

Multiple sclerosis is a chronic disorder of the brain and spinal cord (central nervous system) that causes muscle weakness, poor coordination, numbness, and a variety of other health problems. Several variations of HLA-DQB1 appear to increase the risk of developing this disorder. One of these variations, HLA-DQB1*06:02, is the same version of the gene that increases the risk of narcolepsy.

Some evidence suggests that the HLA-DQB1 gene may also play a role in several forms of pemphigus, a condition that causes severe blistering of the skin and mucous membranes (such as the moist lining of the mouth).

It is unclear how different versions of the HLA-DQB1 gene influence the risk of developing autoimmune disorders. These disorders typically result from a combination of multiple environmental and genetic factors. Changes in other HLA and non-HLA genes, some of which remain unknown, also likely contribute to the risk of developing these complex conditions.

Other Names for This Gene

• CELIAC1
• DQB1_HUMAN
• HLA class II histocompatibility antigen, DQ beta 1 chain
• HLA-DQB
• IDDM1
• major histocompatibility complex class II beta
• MHC class II antigen DQB1
• MHC class II antigen HLA-DQ-beta-1
• MHC class II DQ beta chain
• MHC class II HLA-DQ beta glycoprotein
• MHC class2 antigen
• MHC DQ beta

Genomic Location

Normal Function

The HLA-DRB1 gene provides instructions for making a protein that plays a critical role in the immune system. The HLA-DRB1 gene is part of a family of genes called the human leukocyte antigen (HLA) complex. The HLA complex helps the immune system distinguish the body's own proteins from proteins made by foreign invaders such as viruses and bacteria.

The HLA complex is the human version of the major histocompatibility complex (MHC), a gene family that occurs in many species. The HLA-DRB1 gene belongs to a group of MHC genes called MHC class II. MHC class II genes provide instructions for making proteins that are present on the surface of certain immune system cells. These proteins attach to protein fragments (peptides) outside the cell. MHC class II proteins display these peptides to the immune system. If the immune system recognizes the peptides as foreign (such as viral or bacterial peptides), it triggers a response to attack the invading viruses or bacteria.

The protein produced from the HLA-DRB1 gene, called the beta chain, attaches (binds) to another protein called the alpha chain, which is produced from the HLA-DRA gene. Together, they form a functional protein complex called the HLA-DR antigen-binding heterodimer. This complex displays foreign peptides to the immune system to trigger the body's immune response.

Each MHC class II gene has many possible variations, allowing the immune system to react to a wide range of foreign invaders. Researchers have identified hundreds of different versions (alleles) of the HLA-DRB1 gene, each of which is given a particular number (such as HLA-DRB1*04:01).

Health Conditions Related to Genetic Changes

Alopecia areata

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Autoimmune Addison disease

Certain variations in the HLA-DRB1 gene have been linked to an increased risk of developing an autoimmune disorder called autoimmune Addison disease. Autoimmune disorders occur when the immune system malfunctions and attacks the body's tissues and organs. In autoimmune Addison disease, the immune system attacks the adrenal glands, which are small hormone-producing glands located on top of each kidney. Loss of hormones produced by the adrenal glands leads to the features of the condition, which include extreme tiredness (fatigue), nausea, low blood pressure (hypotension), and abnormally dark areas of skin (hyperpigmentation), especially in regions that experience a lot of friction such as the armpits, elbows, and knuckles. A particular HLA-DRB1 gene variant called HLA-DRB1*04:04 is the most well-known risk factor for autoimmune Addison disease.

Normally, the immune system responds only to proteins made by foreign invaders, not to the body's own proteins. In autoimmune Addison disease, however, an immune response is triggered by a normal adrenal gland protein; in about 85 percent of people with autoimmune Addison disease, the protein is 21-hydroxylase. 21-hydroxylase is found in the adrenal glands where it plays a key role in producing a variety of hormones that regulate many essential functions in the body. The prolonged immune attack triggered by 21-hydroxylase damages the adrenal glands (specifically the outer layers of the glands known, collectively, as the adrenal cortex), preventing hormone production. A shortage of adrenal hormones (adrenal insufficiency) disrupts several normal functions in the body, leading to the diverse features of autoimmune Addison disease. It is not clear how HLA-DRB1*04:04 and other HLA-DRB1 variations are involved in the inappropriate immune response that causes autoimmune Addison disease.

Crohn's disease

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Graves' disease

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Hashimoto's disease

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Idiopathic inflammatory myopathy

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Idiopathic pulmonary fibrosis

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Juvenile idiopathic arthritis

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Lyme disease

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Multiple sclerosis

Variations in the HLA-DRB1 gene have been associated with an increased risk of developing multiple sclerosis. This condition affects the brain and spinal cord (central nervous system), causing muscle weakness, poor coordination, numbness, and a variety of other health problems. One variant of this gene, called HLA-DRB1*15:01, is the most strongly linked genetic factor for the risk of multiple sclerosis.

Because the HLA-DRB1 gene is involved in the immune system, changes in it might be related to the autoimmune response and inflammation that damage nerves and the protective coating surrounding them (the myelin sheath), leading to the signs and symptoms of multiple sclerosis. However, it is unclear exactly what role HLA-DRB1 gene variants play in development of multiple sclerosis. A combination of genetic and environmental factors is likely involved in this condition.

Narcolepsy

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Psoriatic arthritis

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Rheumatoid arthritis

Several common variations of the HLA-DRB1 gene are associated with a person's risk of developing rheumatoid arthritis. This disease causes chronic abnormal inflammation that primarily affects the joints. HLA-DRB1 is one of several genes in the HLA complex that have been associated with rheumatoid arthritis; variations of this gene are the most significant known genetic risk factor for the disease.

The HLA-DRB1 gene variations associated with an increased risk of rheumatoid arthritis affect single protein building blocks (amino acids) in the beta chain. These changes occur near the antigen-recognizing binding groove, which is the part of the protein that attaches (binds) to viral or bacterial peptides. This binding triggers the immune response that attacks foreign invaders. Although the mechanism by which HLA-DRB1 gene variations increase the risk of rheumatoid arthritis is unclear, researchers suspect it is related to changes in peptide binding that stimulate an abnormal immune response. However, many other genetic and environmental factors also contribute to a person's overall risk of developing rheumatoid arthritis.

A few variations of the HLA-DRB1 gene appear to decrease the risk of developing rheumatoid arthritis. It is unclear why these particular changes may be protective.

Rosacea

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Type 1 diabetes

Combinations of variations in the HLA-DRB1 gene and other HLA genes affect the risk of type 1 diabetes. Type 1 diabetes is characterized by high levels of blood glucose, also called blood sugar, resulting from a shortage of the hormone insulin and is caused by autoimmune damage to insulin-producing cells in the pancreas.

Type 1 diabetes risk is most increased by two specific combinations of variations of the HLA-DRB1 gene and other HLA genes called HLA-DQA1 and HLA-DQB1. Combinations of HLA gene variants are called HLA haplotypes. One haplotype, written as DRB1*03:01-DQA1*05:01-DQB1*02, is called DR3. The other haplotype, written as DRB1*04:01/02/04/05/08-DQA1*03:01-DQB1*02, is called DR4. People at highest risk of developing type 1 diabetes have one copy of the DR3 haplotype and one copy of the DR4 haplotype in each cell. Other HLA haplotypes only mildly increase the risk of type 1 diabetes, while some haplotypes seem to protect against developing this condition. Variations in other genes and environmental factors are also thought to affect the risk of this complex disorder.

Autoimmune disorders

Normal variations of the HLA-DRB1 gene have been associated with many other autoimmune disorders, including pemphigus, sarcoidosis, and others listed on this page. Pemphigus is a condition that causes severe blistering of the skin and mucous membranes (such as the moist lining of the mouth). Sarcoidosis is a disorder in which inflammation occurs in many organs and tissues of the body.

It is unclear how different versions of the HLA-DRB1 gene influence the risk of developing autoimmune disorders. These disorders typically result from a combination of multiple environmental and genetic factors. Changes in other HLA and non-HLA genes, some of which remain unknown, also likely contribute to the risk of developing these complex conditions.

Other Names for This Gene

• 2B13_HUMAN
• 2B1F_HUMAN
• 2B1G_HUMAN
• DRB1
• DRw10
• DW2.2/DR2.2
• HLA class II histocompatibility antigen, DR-1 beta chain
• HLA-DR1B
• HLA-DRB
• human leucocyte antigen DRB1
• lymphocyte antigen DRB1
• major histocompatibility complex, class II, DR beta 1 precursor
• MHC class II antigen
• MHC class II HLA-DR beta 1 chain
• MHC class II HLA-DR-beta cell surface glycoprotein
• MHC class II HLA-DRw10-beta
• SS1

Genomic Location

Narcolepsy is a lifelong problem, but it does not usually worsen as the person ages. Symptoms can partially improve over time, but they will never disappear completely. The most typical symptoms are:

• Excessive daytime sleepiness (EDS)—All individuals with narcolepsy have EDS, and it is often the most obvious symptom. EDS is characterized by persistent sleepiness, regardless of how much sleep an individual gets at night. However, sleepiness in narcolepsy is more like a “sleep attack,” where an overwhelming sense of sleepiness comes on quickly. In between sleep attacks, individuals have normal levels of alertness, particularly if doing activities that keep their attention.
• Cataplexy—This sudden loss of muscle tone while a person is awake leads to weakness and a loss of voluntary muscle control. It is often triggered by sudden, strong emotions such as laughter, fear, anger, stress, or excitement. The symptoms of cataplexy may appear weeks or even years after the onset of EDS. Some people may only have one or two attacks in a lifetime, while others may experience many attacks a day. In about 10 percent of cases of narcolepsy, cataplexy is the first symptom to appear and can be misdiagnosed as a seizure disorder. Attacks may be mild and involve only a momentary sense of minor weakness in a limited number of muscles, such as a slight drooping of the eyelids. The most severe attacks result in a total body collapse during which individuals are unable to move, speak, or keep their eyes open. But even during the most severe episodes, people remain fully conscious, a characteristic that distinguishes cataplexy from fainting or seizure disorders. The loss of muscle tone during cataplexy resembles paralysis of muscle activity that naturally occurs during REM sleep. Episodes last a few minutes at most and resolve almost instantly on their own. While scary, the episodes are not dangerous as long as the individual finds a safe place in which to collapse.
• Sleep paralysis—The temporary inability to move or speak while falling asleep or waking up usually lasts only a few seconds or minutes and is similar to REM-induced inhibitions of voluntary muscle activity. Sleep paralysis resembles cataplexy except it occurs at the edges of sleep. As with cataplexy, people remain fully conscious. Even when severe, cataplexy and sleep paralysis do not result in permanent dysfunction—after episodes end, people rapidly recover their full capacity to move and speak.
• Hallucinations—Very vivid and sometimes frightening images can accompany sleep paralysis and usually occur when people are falling asleep or waking up. Most often the content is primarily visual, but any of the other senses can be involved.

Additional symptoms include:

• Fragmented sleep and insomnia—While individuals with narcolepsy are very sleepy during the day, they usually also experience difficulties staying asleep at night. Sleep may be disrupted by insomnia, vivid dreaming, sleep apnea, acting out while dreaming, and periodic leg movements.
• Automatic behaviors—Individuals with narcolepsy may experience temporary sleep episodes that can be very brief, lasting no more than seconds at a time. A person falls asleep during an activity (e.g., eating, talking) and automatically continues the activity for a few seconds or minutes without conscious awareness of what they are doing. This happens most often while people are engaged in habitual activities such as typing or driving. They cannot recall their actions, and their performance is almost always impaired. Their handwriting may, for example, degenerate into an illegible scrawl, or they may store items in bizarre locations and then forget where they placed them. If an episode occurs while driving, individuals may get lost or have an accident. People tend to awaken from these episodes feeling refreshed, finding that their drowsiness and fatigue has temporarily subsided.

A clinical examination and detailed medical history are essential for diagnosis and treatment of narcolepsy. Individuals may be asked by their doctor to keep a sleep journal noting the times of sleep and symptoms over a one- to two-week period. A physical exam can rule out or identify other neurological conditions that may be causing the symptoms.

Two specialized tests, which can be performed in a sleep disorders clinic, are required to establish a diagnosis of narcolepsy:

1. Polysomnogram (PSG or sleep study)—The PSG is an overnight recording of brain and muscle activity, breathing, and eye movements. A PSG can help reveal whether REM sleep occurs early in the sleep cycle and if an individual's symptoms result from another condition such as sleep apnea.
2. Multiple sleep latency test (MSLT)—The MSLT assesses daytime sleepiness by measuring how quickly a person falls asleep and whether they enter REM sleep.

Occasionally, it may be helpful to measure the level of hypocretin in the fluid that surrounds the brain and spinal cord. To perform this test, a doctor will withdraw a sample of the cerebrospinal fluid using a lumbar puncture (also called a spinal tap) and measure the level of hypocretin-1.

Although there is no cure for narcolepsy, some of the symptoms can be treated with medicines and lifestyle changes.

Medications

• Modafinil—The initial line of treatment is usually a central nervous system stimulant such as modafinil. Modafinil is usually prescribed first because it is less addictive and has fewer side effects than older stimulants. For most people these drugs are generally effective at reducing daytime drowsiness and improving alertness.
• Amphetamine-like stimulants—In cases where modafinil is not effective, doctors may prescribe amphetamine-like stimulants such as methylphenidate to alleviate EDS. However, these medications must be carefully monitored because they can have side effects.
• Antidepressants—Two classes of antidepressant drugs have proven effective in controlling cataplexy in many individuals: tricyclics (including imipramine, desipramine, clomipramine, and protriptyline) and selective serotonin and noradrenergic reuptake inhibitors (including venlafaxine, fluoxetine, and atomoxetine).
• Sodium oxybate—Sodium oxybate (also known as gamma hydroxybutyrate or GHB) has been approved by the U.S. Food and Drug Administration (FDA) to treat cataplexy and excessive daytime sleepiness in individuals with narcolepsy. Due to safety concerns associated with the use of this drug, the distribution of sodium oxybate is tightly restricted.
• Histamine 3 receptor antagonist/inverse agonist—Pitolisant was recently approved by FDA as the only non-scheduled product for treating excessive daytime sleepiness or cataplexy in adults with narcolepsy. Pitolisant, which has been commercially available in the U.S. since 2019, is thought to increase histamine levels in the brain. The most common adverse reactions to Pitolisant are insomnia, nausea, and anxiety.

Lifestyle changes

Drug therapy should accompany various lifestyle changes. Remembering the following seven tips may be helpful:

1. Take short naps. Many individuals take short, regularly scheduled naps at times when they tend to feel sleepiest.
2. Maintain a regular sleep schedule. Going to bed and waking up at the same time every day, even on the weekends, can help people sleep better.
3. Avoid caffeine or alcohol before bed. Individuals should avoid alcohol and caffeine for several hours before bedtime.
4. Avoid smoking, especially at night.
5. Exercise daily. Exercising for at least 20 minutes per day at least four or five hours before bedtime also improves sleep quality and can help people with narcolepsy avoid gaining excess weight.
6. Avoid large, heavy meals right before bedtime. Eating very close to bedtime can make it harder to sleep.
7. Relax before bed. Relaxing activities such as a warm bath before bedtime can help promote sleepiness. Also make sure the sleep space is cool and comfortable.

Safety precautions, particularly when driving, are important for everyone with narcolepsy. Suddenly falling asleep or losing muscle control can transform actions that are ordinarily safe, such as walking down a long flight of stairs, into hazards.

The Americans with Disabilities Act (ADA) requires employers to provide reasonable accommodations for all employees with disabilities. Adults with narcolepsy can often negotiate with employers to modify their work schedules so they can take naps when necessary and perform their most demanding tasks when they are most alert.

Similarly, children and adolescents with narcolepsy may be able to work with school administrators to accommodate special needs, like taking medications during the school day, modifying class schedules to fit in a nap, and other strategies.

Additionally, support groups can be extremely beneficial for people with narcolepsy.

The mission of the National Institute of Neurological Disorders and Stroke (NINDS) is to seek fundamental knowledge about the brain and nervous system and to use that knowledge to reduce the burden of neurological disease. The NINDS, a component of the National Institutes of Health (NIH), along with several other NIH Institutes and Centers, supports research on narcolepsy and other sleep disorders through grants to medical institutions across the country.

Additionally, the National Heart, Lung, and Blood Institute (NHLBI) manages the National Center on Sleep Disorders Research (NCSDR), which coordinates federal government sleep research activities, promotes doctoral and postdoctoral training programs, and educates the public and health care professionals about sleep disorders.

Genetics and biochemicals
NINDS-sponsored researchers are conducting studies devoted to further clarifying the wide range of genetic—both HLA genes and non-HLA genes—and environmental factors that may cause narcolepsy. Other investigators are using animal models to better understand hypocretin and other chemicals such as glutamate that may play a key role in regulating sleep and wakefulness. Researchers are also investigating wake-promoting compounds to widen the range of available therapeutic options and create treatment options that reduce undesired side effects and decrease the potential for abuse. A greater understanding of the complex genetic and biochemical bases of narcolepsy will eventually lead to new therapies to control symptoms and may lead to a cure.

Immune system
Abnormalities in the immune system may play an important role in the development of narcolepsy. NINDS-sponsored scientists have demonstrated the presence of unusual immune system activity in people with narcolepsy. Further, strep throat and certain varieties of influenza are now thought to be triggers in some at-risk individuals. Other NINDS researchers are also working to understand why the immune system destroys hypocretin neurons in narcolepsy in the hopes of finding a way to prevent or cure the disorder.

Sleep biology
NINDS continues to support investigations into the basic biology of sleep, such as examining the brain mechanisms involved in generating and regulating REM sleep and other sleep behaviors. Since sleep and circadian rhythms are controlled by networks of neurons in the brain, NINDS researchers are also examining how neuronal circuits function in the body and contribute to sleep disorders like narcolepsy. A more comprehensive understanding of the complex biology of sleep will give scientists a better understanding of the processes that underlie narcolepsy and other sleep disorders.