HLA antigens in narcolepsy and idiopathic central nervous system hypersomnolence

Association between idiopathic hypersomnia and a genetic variant in the PER3 gene

We aim to identify genetic markers associated with idiopathic hypersomnia, a disabling orphan central nervous system disorder of hypersomnolence that is still poorly understood. In our study, DNA was extracted from 79 unrelated patients diagnosed with idiopathic hypersomnia with long sleep time at the National Reference Center for Narcolepsy-France according to very stringent diagnostic criteria. Whole exome sequencing on the first 30 patients with idiopathic hypersomnia (25 females and 5 males) allowed the single nucleotide variants to be compared with a control population of 574 healthy subjects from the French Exome project database. We focused on the identification of genetic variants among 182 genes related to the regulation of sleep and circadian rhythm. Candidate variants obtained by exome sequencing analysis were then validated in a second sample of 49 patients with idiopathic hypersomnia (37 females and 12 males). Our study characterised seven variants from six genes significantly associated with idiopathic hypersomnia compared with controls. A targeted sequencing analysis of these seven variants on 49 other patients with idiopathic hypersomnia confirmed the relative over-representation of the A➔C variant of rs2859390, located in a potential splicing-site of PER3 gene. Our findings support a genetic predisposition and identify pathways involved in the pathogeny of idiopathic hypersomnia. A variant of the PER3 gene may predispose to idiopathic hypersomnia with long sleep time.

Retrospective multicenter matched case-control study on the risk factors for narcolepsy with special focus on vaccinations (including pandemic influenza vaccination) and infections in Germany

OBJECTIVE

Studies associate pandemic influenza vaccination with narcolepsy. In Germany, a retrospective, multicenter, matched case-control study was performed to identify risk factors for narcolepsy, particularly regarding vaccinations (seasonal and pandemic influenza vaccination) and infections (seasonal and pandemic influenza) and to quantify the detected risks.

METHODS

Patients with excessive daytime sleepiness who had been referred to a sleep center between April 2009 and December 2012 for multiple sleep latency test (MSLT) were eligible. Case report forms were validated according to the criteria for narcolepsy defined by the Brighton Collaboration (BC). Confirmed cases of narcolepsy (BC level of diagnostic certainty 1-4a) were matched with population-based controls by year of birth, gender, and place of residence. A second control group was established including patients in whom narcolepsy was definitely excluded (test-negative controls).

RESULTS

A total of 103 validated cases of narcolepsy were matched with 264 population-based controls. The second control group included 29 test-negative controls. A significantly increased odd ratio (OR) to develop narcolepsy (crude OR [cOR] = 3.9, 95% confidence interval [CI] = 1.8-8.5; adjusted OR [aOR] = 4.5, 95% CI = 2.0-9.9) was detected in individuals immunized with pandemic influenza A/H1N1/v vaccine prior to symptoms onset as compared to nonvaccinated individuals. Using test-negative controls, in individuals immunized with pandemic influenza A/H1N1/v vaccine prior to symptoms onset, a nonsignificantly increased OR of narcolepsy was detected when compared to nonvaccinated individuals (whole study population, BC levels 1-4a: cOR = 1.9, 95% CI = 0.5-6.9; aOR = 1.8, 95% CI = 0.3-10.1).

CONCLUSIONS

The findings of this study support an increased risk for narcolepsy after immunization with pandemic influenza A/H1N1/v vaccine.

Narcolepsy-Associated HLA Class I Alleles Implicate Cell-Mediated Cytotoxicity

STUDY OBJECTIVES

Narcolepsy with cataplexy is tightly associated with the HLA class II allele DQB1*06:02. Evidence indicates a complex contribution of HLA class II genes to narcolepsy susceptibility with a recent independent association with HLA-DPB1. The cause of narcolepsy is supposed be an autoimmune attack against hypocretin-producing neurons. Despite the strong association with HLA class II, there is no evidence for CD4+ T-cell-mediated mechanism in narcolepsy. Since neurons express class I and not class II molecules, the final effector immune cells involved might include class I-restricted CD8+ T-cells.

METHODS

HLA class I (A, B, and C) and II (DQB1) genotypes were analyzed in 944 European narcolepsy with cataplexy patients and in 4,043 control subjects matched by country of origin. All patients and controls were DQB1*06:02 positive and class I associations were conditioned on DQB1 alleles.

RESULTS

HLA-A*11:01 (OR = 1.49 [1.18-1.87] P = 7.0*10(-4)), C*04:01 (OR = 1.34 [1.10-1.63] P = 3.23*10(-3)), and B*35:01 (OR = 1.46 [1.13-1.89] P = 3.64*10(-3)) were associated with susceptibility to narcolepsy. Analysis of polymorphic class I amino-acids revealed even stronger associations with key antigen-binding residues HLA-A-Tyr(9) (OR = 1.32 [1.15-1.52] P = 6.95*10(-5)) and HLA-C-Ser(11) (OR = 1.34 [1.15-1.57] P = 2.43*10(-4)).

CONCLUSIONS

Our findings provide a genetic basis for increased susceptibility to infectious factors or an immune cytotoxic mechanism in narcolepsy, potentially targeting hypocretin neurons.

Central Disorders of Hypersomnolence: Focus on the Narcolepsies and Idiopathic Hypersomnia

The central disorders of hypersomnolence are characterized by severe daytime sleepiness, which is present despite normal quality and timing of nocturnal sleep. Recent reclassification distinguishes three main subtypes: narcolepsy type 1, narcolepsy type 2, and idiopathic hypersomnia (IH), which are the focus of this review. Narcolepsy type 1 results from loss of hypothalamic hypocretin neurons, while the pathophysiology underlying narcolepsy type 2 and IH remains to be fully elucidated. Treatment of all three disorders focuses on the management of sleepiness, with additional treatment of cataplexy in those patients with narcolepsy type 1. Sleepiness can be treated with modafinil/armodafinil or sympathomimetic CNS stimulants, which have been shown to be beneficial in randomized controlled trials of narcolepsy and, quite recently, IH. In those patients with narcolepsy type 1, sodium oxybate is effective for the treatment of both sleepiness and cataplexy. Despite these treatments, there remains a subset of hypersomnolent patients with persistent sleepiness, in whom alternate therapies are needed. Emerging treatments for sleepiness include histamine H3 antagonists (eg, pitolisant) and possibly negative allosteric modulators of the gamma-aminobutyric acid-A receptor (eg, clarithromycin and flumazenil).

Risk of narcolepsy associated with inactivated adjuvanted (AS03) A/H1N1 (2009) pandemic influenza vaccine in Quebec

Context

An association between an adjuvanted (AS03) A/H1N1 pandemic vaccine and narcolepsy has been reported in Europe.

Objective

To assess narcolepsy risk following administration of a similar vaccine in Quebec.

Design

Retrospective population-based study.

Setting

Neurologists and lung specialists in the province were invited to report narcolepsy cases to a single reference centre.

Population

Patients were interviewed by two sleep experts and standard diagnostic tests were performed. Immunization status was verified in the provincial pandemic influenza vaccination registry.

Main Outcome Measures

Confirmed narcolepsy with or without cataplexy with onset of excessive daytime sleepiness between January 1^st, 2009, and December 31^st, 2010. Relative risks (RRs) were calculated using a Poisson model in a cohort analysis, by a self-controlled case series (SCCS) and a case-control method.

Results

A total of 24 cases were included and overall incidence rate was 1.5 per million person-years. A cluster of 7 cases was observed among vaccinated persons in the winter 2009–2010. In the primary cohort analysis, 16-week post-vaccination RR was 4.32 (95% CI: 1.50–11.12). RR was 2.07 (0.70–6.17) in the SCCS, and 1.48 (0.37–7.03) using the case-control method. Estimates were lower when observation was restricted to the period of pandemic influenza circulation, and tended to be higher in persons <20 years old and for cataplexy cases.

Conclusions

Results are compatible with an excess risk of approximately one case per million vaccine doses, mainly in persons less than 20 years of age. However, a confounding effect of the influenza infection cannot be ruled out.

Idiopathic hypersomnia: a report of three adolescent-onset cases in a two-generation family

Idiopathic hypersomnia is an uncommon sleep disorder characterized by prolonged sleep time and excessive daytime sleepiness without cataplexy. This study concerned a case of familial occurrence. The proband expressed an idiopathic hypersomnia with long sleep time at the age of 12 years. Clinical interview and ad libitum polysomnographic study did not reveal any symptoms of narcolepsy or other sleep disorders. Family history revealed that a 20-year-old sister had experienced symptoms of hypersomnia from the age of 16 and their mother had been diagnosed with idiopathic hypersomnia previously. The diagnosis of idiopathic hypersomnia with long sleep time was confirmed in the sister by clinical interview and ad libitum polysomnography. Human leukocyte antigen (HLA) did not reveal the DQB1-0602 phenotype in the proband and relatives. This report confirms the hypothesis of a genetic predisposition in idiopathic hypersomnia.

Idiopathic hypersomnia: a study of 77 cases

STUDY OBJECTIVES

To review the clinical and polysomnographic characteristics of idiopathic hypersomnia as well as the long-term response to treatment.

SETTING

The Respiratory Support and Sleep Centre at Papworth Hospital, Cambridge, UK.

PATIENTS AND DESIGN

A large database of more than 6000 patients with sleep disorders was reviewed. A retrospective study of the clinical and polysomnographic characteristics of 77 patients with idiopathic hypersomnia was performed. Comparison with a similar group of patients with narcolepsy was performed. The response to drug treatment was assessed in 61 patients over a mean follow-up of 3.8 years.

MEASUREMENTS AND RESULTS

Idiopathic hypersomnia was 60% as prevalent as narcolepsy. Comparison with a similar group of patients with narcolepsy showed that those with idiopathic hypersomnia were more likely to have prolonged unrefreshing daytime naps, a positive family history, increased slow-wave sleep, and a longer sleep latency on the Multiple Sleep Latency Test. The results of the Multiple Sleep Latency Test were not helpful in predicting disease severity or treatment response. The clinical features were heterogeneous and of variable severity. The majority of patients with idiopathic hypersomnia had symptoms that remained stable over many years, but 11% had spontaneous remission, which was never seen in narcolepsy. Two thirds of patients with idiopathic hypersomnolence had a sustained improvement in daytime somnolence with medication, although a third needed high doses or combinations of drugs.

CONCLUSIONS

Idiopathic hypersomnolence has characteristic clinical and polysomnographic features but the prolonged latency on the Multiple Sleep Latency Test raises doubt about the validity of this test within the current diagnostic criteria. The disease often responds well to treatment and a substantial minority of patients appear to spontaneously improve.

Clinical and neurobiological aspects of narcolepsy

Narcolepsy is characterized by excessive daytime sleepiness (EDS), cataplexy and/or other dissociated manifestations of rapid eye movement (REM) sleep (hypnagogic hallucinations and sleep paralysis). Narcolepsy is currently treated with amphetamine-like central nervous system (CNS) stimulants (for EDS) and antidepressants (for cataplexy). Some other classes of compounds such as modafinil (a non-amphetamine wake-promoting compound for EDS) and gamma-hydroxybutyrate (GHB, a short-acting sedative for EDS/fragmented nighttime sleep and cataplexy) given at night are also employed. The major pathophysiology of human narcolepsy has been recently elucidated based on the discovery of narcolepsy genes in animals. Using forward (i.e., positional cloning in canine narcolepsy) and reverse (i.e., mouse gene knockout) genetics, the genes involved in the pathogenesis of narcolepsy (hypocretin/orexin ligand and its receptor) in animals have been identified. Hypocretins/orexins are novel hypothalamic neuropeptides also involved in various hypothalamic functions such as energy homeostasis and neuroendocrine functions. Mutations in hypocretin-related genes are rare in humans, but hypocretin-ligand deficiency is found in many narcolepsy-cataplexy cases. In this review, the clinical, pathophysiological and pharmacological aspects of narcolepsy are discussed.

Association of HLA-DR and -DQ genes with narcolepsy in Koreans: comparison with two control groups, randomly selected subjects and DRB1*1501-DQB1*0602--positive subjects

The purpose of this study was to investigate the association of human leukocyte antigen (HLA) class II alleles with narcolepsy-cataplexy susceptibility in Koreans. The distribution of HLA-DRB1 and -DQB1 alleles and presence or absence of DRB3/4/5 alleles were examined in 60 narcoleptic patients with clear-cut cataplexy, and the results were compared with two groups of healthy controls: 200 randomly selected controls and 144 DRB1*1501-DQB1*0602 positive controls. All of the narcoleptic patients were DRB1*1501 and DQB1*0602 positive, and their frequencies were significantly higher in patients than in random controls (100% vs 17.0%, p(c) = 2.3 x 10(-30), OR = 583.96; 100% vs 16.5%, p(c) = 3.9 x 10(-31), OR = 605.00). The HLA association in Koreans was as tight as that reported in Japanese. Several DRB1 (*0101, *0405, *0901) and DQB1 alleles (*0303, *0401, *0501, *0601, *0604) were found to have weak protective effects against narcolepsy. DRB4 showed strong protective effect, and this was also significant when compared with DRB1*1501-DQB1*0602 positive controls (18.3% vs 44.4%, p(c) = 0.001, OR = 0.28). DRB3 (OR = 1.86) and DQB1*0301 (OR = 2.45) were found to have weak predisposing effect, when compared with DRB1*1501-DQB1*0602 positive controls. The protective effect of DRB4 has to be further studied in other populations.

Narcolepsy: a review of evidence for autoimmune diathesis

Sporadic narcolepsy with cataplexy is a disabling disease that is strongly associated with the major histocompatibility class II allele HLA DQB1*0602 and is characterized by profound reduction in the cerebrospinal fluid (CSF) concentration of hypocretin 1 levels. This article provides a comprehensive review of the evidence that neurologic autoimmunity is the pathogenic basis of narcolepsy with cataplexy. Despite this evidence, specific antibody markers for narcolepsy have been elusive. Clinical trials using intravenous immunoglobulin infusions in recent onset narcolepsy with cataplexy have led to improvement in cataplexy in some patients. Future research must focus on elucidation of immune markers and early ameliorative treatments for narcolepsy.

Narcolepsy and Disorders of Excessive Somnolence

Recent studies provide valid criteria that help differentiate idiopathic narcolepsy from other disorders of excessive daytime somnolence [3]. Research to date suggests that idiopathic narcolepsy might properly be considered a disorder of excessive sleepiness with dysfunctional REM-sleep mechanisms, clinically evidenced as cataplexy and electrophysiologically recognized as SOREMPs. Given these criteria, a diagnosis can generally be made using a combination of history, PSG, and MSLT. Traditionally, the medical treatment of idiopathic narcolepsy has centered on a two-drug regimen (stimulants for sleepiness and TCAs for cataplexy and auxiliary symptoms). Some newer medications are proving efficacious for sleepiness with minimal adverse effects, whereas others may provide a single-drug regimen that simultaneously addresses sleepiness and cataplexy [18]. New research has allowed some experts to hypothesize that idiopathic narcolepsy may be the result of a genetic predisposition to autoimmune disease [176]. It is possible that aberrant genetic coding of elements in the hypocretin/orexin systems allows a sensitivity to inducible and possibly virally mediated changes, which leave cells in the lateral hypothalamus susceptible to autoimmune attack [96]. As such, genetic screening of high-risk individuals might eventually rationalize the prophylactic use of immunosuppressants in some instances. In the future, for atypical cases(poorly responsive to therapy), genetic, CSF, and brain imaging studies, and possibly even neuronal transplantation may prove beneficial in the assessment and treatment of idiopathic narcolepsy.

Clinical aspects and pathophysiology of narcolepsy

Narcolepsy is a chronic debilitating sleep disorder first described in the late 19th century. It is characterized by two major symptoms, excessive daytime sleepiness and cataplexy, and two so-called auxiliary symptoms, hypnagogic hallucinations and sleep paralysis. The final diagnosis relies on polysomnography showing the presence of sleep onset rapid eye movement periods (SOREMPs) during the multiple sleep latency test. The presence of HLA DQA1*0102-DQB1*0602 is supportive of the diagnosis. The pathophysiology of the disorder is still unknown but an imbalance between monoamines and acetylcholine is generally accepted. Recent findings in narcoleptic dogs, a natural model of narcolepsy, and in knockout mice revealed that a mutation of type 2 hypocretin receptor plays a major role in the etiology of narcolepsy. Up to now, no mutation has been found in humans except a case of early onset and atypical narcolepsy. However, a marked reduction of hypocretin type 1 has been found in the cerebrospinal fluid (CSF) of a majority of patients and a global loss of hypocretins was noted in post-mortem brain tissue of narcoleptic subjects. Conversely, no hypocretin neuron degeneration has been observed in the genetic form of narcolepsy in dogs but no trace of hypocretin was seen in the brain or the CSF in cases of sporadic canine narcolepsy. This suggests that different hypocretinergic mechanisms are involved in sporadic and genetic forms of canine narcolepsy. Treatment has not evolved significantly over the last few years. However, new drugs, such as hypocretin agonists, are currently being developed.

SIGNIFICANCE

After the discovery of the type 2 hypocretin receptor mutation in canine narcolepsy and the finding of a CSF hypocretin-1 deficiency in human narcolepsy, the major stream of research has involved the hypocretinergic system. However, other lines of research deserve to be pursued simultaneously, in view of comprehensive advancements in the understanding of narcolepsy.

Narcolepsy and the HLA region

Narcolepsy was first shown to be tightly associated with HLA-DR2 and DQ1 in 1983, suggesting a possible autoimmune mechanism. Early investigations failed to demonstrate this hypothesis, postulating that HLA-DR2 was only a linkage marker for another, unknown narcolepsy-causing gene. The autoimmune hypothesis is now being re-evaluated under the light of recent results. Like many other autoimmune disorders, narcolepsy usually starts during adolescence, is human leukocyte antigen (HLA)-associated, multigenic and environmentally influenced. Furthermore, HLA-association studies indicated a primary HLA-DQ effect with complex HLA class II allele interactions and a partial contribution of HLA to overall genetic susceptibility. Finally, recent result suggests that human narcolepsy is associated with the destruction of a small number of hypothalamic neurons containing the peptide hypocretins (orexins). This data is consistent with an immune destruction of hypocretin-containing cells as the most common etiology for human narcolepsy.

Idiopathic hypersomnia

Identification of idiopathic hypersomnia dates back 20 years only. It typically consists of prolonged nocturnal sleep, great difficulty waking up in the morning or at the end of a nap, and constant or recurrent excessive daytime sleepiness. Complete and incomplete forms are encountered. Twenty-three subjects fulfilling ICSD criteria are reported with clinical, polysomnographic and immunogenetic data. Considering differential diagnosis is an important step in the diagnosis of idiopathic hypersomnia. Idiopathic hypersomnia is much less frequent than narcolepsy. A strong genetic component is suggested by the high proportion of familial cases. No association with HLA has been evidenced to date.

Narcolepsy and idiopathic hypersomnolence

Narcolepsy is among the leading causes of excessive daytime sleepiness. Its classic form associates daytime sleepiness with cataplexy, sleep paralysis, hypnopompic hallucinations, and nocturnal disrupted sleep. This form is associated with HLA DQ betal-0602 in about 85% to 90% of affected subjects, independently of their ethnicity. But the definition of the variants of narcolepsy remains controversial, despite the fact that, in some cases, narcolepsy may be limited to daytime sleepiness. In its classic form, it is associated with two or more sleep onset rapid eye movement periods at the Multiple Sleep Latency Test. This test, performed after nocturnal polysomnography, can be helpful in diagnosing narcolepsy, in the absence of a convincing history of partial or complete attacks of cataplexy--a pathognomonic symptom. Investigation of narcoleptic Dobermans has indicated that a muscarinic cholinergic hypersensitivity exists in the brain of affected animals and abnormalities involve also the dopaminergic system. Despite its prevalence of 0.03% to 0.05%, it is still a neurologic entity often missed. Investigations of families of narcoleptics, including monozygotic twins, indicate that this syndrome is polygenic in nature with association of environmental factors. As the peak of onset of disabling symptoms occurs between 15 and 25 years of age, it is important to improve the treatment of this lifelong, disabling illness. Stimulants medications, independently of their mode of action, are prescribed to help daytime sleepiness, and tricyclic antidepressant drugs or serotonergic reuptake blockers are used on the other symptoms. But these medications have a limited efficacy. Short naps at regular intervals during the day are a strong therapeutic adjuvent.

HLA haplotypes, polysomnography, and pedigrees in a case series of patients with narcolepsy

An ongoing study of the genetics of narcolepsy ascertains families through a case series of narcoleptic probands using diagnostic criteria consisting of 1) clinical history of excessive somnolence, 2) a mean sleep latency on the multiple sleep latency test (MSLT) of less than 7.9 minutes, 3) the rapid eye movement (REM) sleep-related symptom of cataplexy, 4) nocturnal polysomnography ruling out sleep apnea syndrome, and 5) two or more transitions to REM sleep on the MSLT. All probands and first-degree relatives received clinical and laboratory evaluations as well as human leukocyte antigen (HLA) typing. Demographic characteristics of the 32 probands are as follows: 17 males and 15 females; mean age was 42.1 years (range 13-70 years). The polysomnographic data confirmed daytime sleepiness and increased tendency for REM sleep for the 32 probands. Nocturnal polysomnographic results are as follows: sleep latency, 3.2 minutes; total sleep time, 442 minutes. MSLT results are as follows: sleep latency, 3.1 minutes; REM latency, 6.9 minutes; number of REM periods, 3.2. HLA typing revealed the presence of the HLA haplotypes, DRB1*15 and DQB1*0602, in 21 narcoleptic probands, with two African-Americans having the DQB1*0602 but not the DRB1*15 allele. Among the 57 relatives of the 32 probands, 1/31 females and 7/26 males were found to be affected with narcolepsy (p < 0.02), which suggests a higher diagnostic rate in male relatives. The 21 probands who were positive for the DRB1*15 and DQB1*0602 haplotypes did not differ from the 10 probands who were negative for these alleles in terms of their nocturnal sleep parameters, MSLT findings, or clinical presentation. Three families with multiple individuals affected with narcolepsy are presented. Two families have more than one affected individual who does not have the high-risk HLA haplotype. In one of these families, the disease is segregating independently of any HLA haplotype. In the third family, there is cosegregation with HLA DRB1*15 and DQB1*0602. One family contains a pair of DNA-confirmed, monozygotic twins with narcolepsy who are discordant for cataplexy and have the HLA DR14(Dw9)/DQB1*0503 and DR4(Dw4)/DQB1*0302 haplotypes.

Extensive HLA class II studies in 58 non-DRB1*15 (DR2) narcoleptic patients with cataplexy

Narcolepsy is a sleep disorder that has been shown to be tightly associated with HLA DR15 (DR2). In this study, 58 non-DR15 patients with narcolepsy-cataplexy were typed at the HLA DRB1, DQA1 and DQB1 loci. Subjects included both sporadic cases and narcoleptic probands from multiplex families. Additional markers studied in the class II region were the promoters of the DQA1 and DQB1 genes, two CA repeat polymorphisms (DQCAR and DQCARII) located between the DQA1 and DQB1 genes, three CA repeat markers (G51152, T16CAR and G411624R) located between DQB1 and DQB3 and polymorphisms at the DQB2 locus. Twenty-one (36%) of these 58 non-DR15 narcoleptic patients were DQA1*0102 and DQB1*0602, a DQ1 subtype normally associated with DRB1*15 in DR2-positive narcoleptic subjects. Additional microsatellite and DQA1 promoter diversity was found in some of these non-DR15 but DQB1*0602-positive haplotypes but the known allele specific codons of DQA1*0102 and DQB1*0602 were maintained in all 21 cases. The 37 non-DQA1*0102/DQB1*0602 subjects did not share any particular HLA DR or DQ alleles. We conclude that HLA DQA1*0102 and DQB1*0602 are the most likely primary candidate susceptibility genes for narcolepsy in the HLA class II region.

Electrophysiological and immunogenetic findings in recurrent monosymptomatic-type hypersomnia: a study of two unrelated Italian cases

MSLT and immunogenetic findings in two unrelated Italian subjects with recurrent monosymptomatic hypersomnia are reported. In both patients MSLT documented a markedly increased daytime sleep propensity during the attacks without augmented REM sleep pressure. Both patients share the same HLA haplotype (HLA-DR1, DQ1) which has been found in Kleine-Levin syndrome. This makes these subtypes of recurrent hypersomnia indistinguishable one from the other, under the immunogenetic profile, but permits differentiation from narcolepsy which is HLA-DR2, DQ1 closely linked.

Idiopathic recurring stupor: a case with possible involvement of the gamma-aminobutyric acid (GABA)ergic system

A patient had recurrent spontaneous episodes of stupor or coma in the absence of toxic, metabolic, or structural brain damage. Ictal electroencephalography showed fast 14 Hz background activity; sleep studies excluded narcolepsy. Flumazenil (Anexate), a benzodiazepine antagonist, promptly resolved the episodes and normalized the electroencephalogram. Radioreceptor binding studies showed the presence of a ligand to the central benzodiazepine receptor in plasma and cerebrospinal fluid during the episodes, suggesting a gamma-aminobutyric acid (GABA)ergic system involvement in the origin of the attacks.

Hypersomnia in dystrophia myotonica: a neurophysiological and immunogenetic study

Ten patients with dystrophia myotonica (8 adults and 2 prepubertal children), from three unrelated families, were investigated for diurnal sleepiness, using a sleep questionnaire and multiple sleep latency test (MSLT). Immunogenetic study was also carried out to assess the involvement of HLA region genes in modulating susceptibility to excessive diurnal sleepiness (EDS). EDS was reported by 5 patients and confirmed in each case by MSLT. In the whole patients group, mean daytime sleep latency was significantly shorter than in healthy controls matched for age and sex. At clinical or neurophysiological evaluation, EDS did not show the features associated with the narcoleptic type. In only one case hypersomnolence could be explained by underlying sleep-disordered breathing. HLA patterns were different from those frequently observed in the narcoleptic or non-narcoleptic types of hypersomnia. In patients with EDS, the frequency of the DQW1 and particularly of the DRW6-DQW1 haplotype appeared to be over-represented.

Narcolepsy update

Narcolepsy, a disorder of excessive daytime sleepiness that affects more than 125,000 people in the United States, is technically defined as a daytime mean sleep latency (time elapsed before falling asleep) of less than 5 minutes in conjunction with verification of rapid eye movement sleep in at least two of five daytime nap periods. Cataplexy, hypnagogic hallucinations, and sleep paralysis are frequently associated with narcolepsy. Currently, overnight polysomnography and multiple sleep latency testing in a sleep disorders laboratory are used to diagnose narcolepsy. Standard pharmacologic therapy consists of the judicious use of stimulants to improve alertness and the administration of tricyclic and other antidepressant drugs to suppress cataplexy. In addition, good sleep hygiene (a regular sleep-wake schedule, an adequate amount of sleep at night, and scheduled daytime naps) is essential for optimal management of this disorder. Patient and family education about narcolepsy and its treatment is also important. Even with use of the best available treatment regimens, many patients with narcolepsy have substantial vocational and social impairments.

HLA class II-restricted binding of muramyl peptides to B lymphocytes of normal and narcoleptic subjects

The propensity for narcolepsy, a clinical sleep disorder of unknown etiology, is virtually totally included within the HLA-DR2,DQw1 (DRw15,DQw6) phenotype. The disorder is characterized by decreased sleep latency, early onset of rapid eye movement sleep, and a paucity of nocturnal slow-wave sleep. Muramyl peptides, naturally occurring bacterial cell wall peptidoglycans, potently enhance the duration and amplitude of slow-wave sleep in animals, bind to murine mononuclear cells, and exhibit a major histocompatibility complex-restricted immunoadjuvant effect in mice. We examined the binding of muramyl peptides to peripheral blood mononuclear leukocytes of HLA-typed normal (n = 13) and narcoleptic (n = 10) subjects. Muramyl peptides bound specifically and with high affinity to normal B- but not T-lymphocyte-enriched preparations. There was no significant specific binding to B-cell-enriched preparations from narcoleptic patients. Furthermore, B-lymphocyte-enriched preparations of normal individuals who had the HLA-DR2,DQw1 phenotype (n = 8) exhibited a lower level of specific binding than those of normals who did not have this phenotype (n = 5, p less than 0.001). These observations are an additional indication of the relevance of muramyl peptides to slow-wave sleep and provide a basis for a better understanding of the relation between narcolepsy and the MHC at the biochemical level.

Familial patterns of narcolepsy

Familial patterns of narcolepsy were investigated in a clinic population of 334 unrelated narcoleptic patients. 40% of probands had at least 1 family member with an isolated daytime sleepiness complaint and 6% had a positive family history of narcolepsy. Multicase families were rare; only two families were found with 3 or more affected relatives. Family members often shared the same HLA-DR2 haplotype as the proband but did not have narcolepsy. However, the risk of disease for first-degree relatives was six to eighteen times greater than that for unrelated individuals. Although most patients were HLA-DR2+, 2 new HLA-DR2- individuals were found. The data predict that as many as 9% of unrelated North-American white patients with narcolepsy will be DR2-. Analysis of these and other data indicates that although strongly associated with disease, the HLA-DR2 haplotype is neither sufficient nor necessary for the development of narcolepsy.

Genetic factors in sleep disorders

Several sleep disorders have a genetic basis. These conditions include the narcoleptic syndrome, sleep walking, periodic movements in sleep, circadian delay syndromes and familial insomnia. These disorders illustrate different control mechanisms involved in sleep and wakefulness, including those determining the prevalence and timing of NREM and REM activity, somatomotor inhibition and excitation, autonomic discharge, and the circadian framework of sleep. The genetic defect in narcolepsy has been localised to the short arm of chromosome 6, but the chromosomal localisations of the genetic basis for the other disorders are not known. Also, with the possible exception of acetylcholine, no definite neurotransmitter involved in any aspect of sleep regulation has been positively identified and the biochemical defect in narcolepsy is not known.

Narcolepsy without unique MHC class II antigen association: studies in the canine model

Human narcolepsy is almost exclusively associated with the major histocompatibility complex (MHC) class II antigen HLA-DR2 and is the strongest HLA-disease association described to date. Canine narcolepsy resembles the human disease in its behavioral manifestations and responses to therapeutic drugs. Therefore, mixed leukocyte culture (MLC) was used to study differences in the canine MHC class II (DLA-D) antigens present in narcoleptic dogs to determine whether an analogous, unique DLA-D antigen could be identified in canine narcolepsy. Results show at least five different DLA-D antigens appear in potential narcoleptic haplotypes among the 29 dogs studied. The data demonstrate that, unlike man, in dogs there is no unique D locus antigen associated with narcolepsy and further suggest that linkage disequilibrium with a specific MHC antigen is unlikely to be essential for the manifestation of canine narcolepsy. Because human narcolepsy is thought to be multigenic, the canine narcolepsy-MHC dissociation suggests that the dog model may help elucidate the non-MHC narcolepsy gene(s).

No difference in the nucleotide sequence of the DQ beta beta 1 domain between narcoleptic and healthy individuals with DR2,Dw2

Narcolepsy is a sleep disorder completely associated with HLA-DR2,Dw2. We demonstrated the 100% presence of three DQ beta fragments (EcoRI 2.4-kb, BamHI 2.9-kb, and PstI 12-kb) in narcoleptic patients that were detected in healthy DR2 controls only at decreased frequencies. In this paper, we have cloned the DQ beta gene from three Japanese narcoleptic patients and sequenced their beta 1 domain in order to study the sequence polymorphisms that might exist in the DQ beta genes of patients, but no difference in sequence could be found between narcoleptic and healthy individuals, suggesting that narcolepsy is not due to mutation in the DQ beta gene. In this context, a possible role of the HLA class II antigens in narcolepsy is discussed.

Compound narcolepsy: sleep pattern and involution

A review of studies of sleep in three-month-old infants, narcoleptics, and normal adults indicates that the sleep pattern in compound narcolepsy is in many ways involuted. Similarities in sleep onsets, REM-specific movement, REM dissociation, ambiguous sleep, nocturnal arousals, diurnal sleep-wake cycles, and relatively limited quiet-awake time are discussed as part of a global inability to inhibit state changes common to both infants and compound narcoleptics. The analogy with infant sleep patterns and results of studies of brain function in narcoleptics suggest that forebrain inhibitory processes are more important in narcoleptic symptomology than is brainstem dysfunction. Puberty and old age are critical periods for the development or exacerbation of the involuted sleep pattern. Closer study of the early development of narcoleptics and of lability of state changes in narcolepsy may aid in diagnosis and prognosis for susceptible individuals.

Compound narcolepsy: development of biochemical imbalance

In a review of existing literature, compound narcolepsy is shown to involve not only problems of sleep regulation, but also autonomic, hormonal, emotional, and possibly motor and cognitive dysfunctions, strongly implicating the hypothalamus, limbic system, and possibly the striatum and cortex in the disorder. Neurochemical studies and the pattern of narcoleptic symptoms support the idea of a dynamic imbalance between dopamine and acetylcholine in the etiology of the disorder. What is known about the natural history of compound narcolepsy suggests a developmental course beginning with fluctuations in dopamine release, followed by supersensitivity of dopamine autoreceptors, and later followed by a pattern of intrinsic oscillations and reciprocal "overshoots" in release of dopamine and acetylcholine to account for the typical sequence of appearance of narcoleptic symptoms.

No male segregation distortion of DR2 haplotypes in Japanese narcoleptic patients

Segregation of narcolepsy-associated DR2/DQw1 haplotypes was studied in 19 informative Japanese families. Each family consisted of a DR2-heterozygous patient, his or her spouse, and their children. In contrast to the previous study on Caucasian narcolepsy, no segregation distortion of the DR2/DQw1 haplotype was observed. The DR2/DQw1 haplotypes were inherited by 9 of 22 offspring from fathers (41%, p = 0.54) and by 10 of 14 offspring from mothers (71%, p = 0.16). These data show that there is no significant segregation distortion of the DR2/DQw1 haplotype in Japanese patients with narcolepsy.

Cellular approach for detecting narcolepsy-specific alterations in DR2 haplotypes

In an attempt to detect disease-associated genetic variations and/or exogenously induced alterations in DR2 haplotypes of narcolepsy patients, primed lymphocytes (PLs) were generated in nine families against DR2 haplotypes of narcolepsy patients and healthy family members. Twenty-four PL reagents were obtained and restimulated by cells of unrelated narcolepsy patients and DR2/Dw2-positive healthy individuals. The mean restimulation rates triggered by cells of patients or healthy controls, respectively, never differed significantly. In primary MLC as well as PLT combinations of patients and their HLA-identical siblings no significant stimulation was observed in both directions. We conclude that narcolepsy-specific alterations of class II molecules cannot be cellularly detected or do not exist on peripheral lymphocytes.

Taq I-generated HLA-DQ alpha polymorphism in Japanese patients with narcolepsy

Taq I-generated HLA-DQ alpha restriction fragment length polymorphism was examined in Japanese patients with narcolepsy. All patients were DR2 positive and shared a 6.0 kb fragment, although this fragment was found only in 54% of the healthy DR2-positive Japanese. This finding added the DQ alpha gene to the list of candidates for the possible narcolepsy-susceptibility gene. In contrast, there was no complete association between narcolepsy and DX alpha restriction fragment length polymorphism. These findings suggest that a narcolepsy-susceptibility gene is located closer to the DQ locus than to the DX locus.

Possible male segregation distortion of DR2 haplotypes in narcolepsy patients

Segregation of disease-associated DR2-linked haplotypes from patients with narcolepsy was studied in 18 German families. Of these, 13 were informative, as transmission could be traced from DR2 heterozygous patients to their healthy offspring. Although the composition of extended haplotypes was equal in males and females, DR2 was transmitted to 78.6% of the offspring by diseased fathers but only to 57.1% by diseased mothers. Compared to an expected 1:1 ratio according to Mendelian segregation this means a statistically significant deviation (p less than or equal to 0.03) for male but not for female patients. In contrast, transmission distortion was not observed with 30 DR2 haplotypes in 27 healthy families. These data represent a new example of male segregation distortion in an HLA-associated disorder.

Diagnostic criteria for narcolepsy and HLA-DR2 frequencies

HLA-DR2 frequencies were investigated in Japanese patients with narcolepsy as defined by various diagnostic criteria. The DR2 frequency was 100% when our criteria for narcolepsy were employed. The use of other criteria that lacked cataplexy as an obligatory symptom, however, reduced the DR2 frequency and led to an apparent "discovery" of DR2-negative cases with "narcolepsy". This observation indicates the necessity of precise diagnostic criteria in research on the HLA-narcolepsy association.

The occurrence of HLA-DR2 in clinically established narcolepsy

Of 25 patients with a longstanding diagnosis of narcolepsy 23 were HLA-DR2 positive. The 2 DR2 negative patients were misdiagnosed when retrospectively interviewed. HLA-DR2 determination is a valuable tool for ascertaining the narcolepsy diagnosis in uncertain cases.

HLA-DR2 in childhood narcolepsy

A 6-year-old boy with behavioral changes was found to have clinical and electrographically defined narcolepsy. He has HLA-DR2 as do virtually all adult narcoleptics. This finding raises new diagnostic, etiopathogenetic, and future therapeutic issues.