Epidemiology and Pathophysiology of Childhood Narcolepsy

Sleep Disorders in Childhood

OBJECTIVE

This article provides a comprehensive review of pediatric sleep disorders including the clinical features, diagnosis, and treatment of sleep-disordered breathing, insomnia, parasomnias, restless sleep disorder, restless legs syndrome, narcolepsy in childhood, and Kleine-Levin syndrome.

LATEST DEVELOPMENTS

Our understanding of pediatric sleep pathophysiology continues to evolve, and diagnostic and treatment modalities have expanded. A low-sodium oxybate formulation was approved in July 2020 in the United States to treat cataplexy and excessive daytime sleepiness in patients 7 years old and older with narcolepsy. A validated pediatric hypersomnolence survey for pediatric narcolepsy and idiopathic hypersomnia with high sensitivity, specificity, and interrater reliability is now available.

ESSENTIAL POINTS

The clinical presentation, diagnostics, and treatment of children with sleep disorders differ from those of adults. Untreated sleep disorders in childhood can lead to adverse physical and psychological consequences in adults. Correctly diagnosing and treating sleep disorders in youth can prevent a significant burden of disease in adulthood.

Narcolepsy-A Neuropathological Obscure Sleep Disorder: A Narrative Review of Current Literature

Narcolepsy is a chronic, long-term neurological disorder characterized by a decreased ability to regulate sleep-wake cycles. Some clinical symptoms enter into differential diagnosis with other neurological diseases. Excessive daytime sleepiness and brief involuntary sleep episodes are the main clinical symptoms. The majority of people with narcolepsy experience cataplexy, which is a loss of muscle tone. Many people experience neurological complications such as sleep cycle disruption, hallucinations or sleep paralysis. Because of the associated neurological conditions, the exact pathophysiology of narcolepsy is unknown. The differential diagnosis is essential because relatively clinical symptoms of narcolepsy are easy to diagnose when all symptoms are present, but it becomes much more complicated when sleep attacks are isolated and cataplexy is episodic or absent. Treatment is tailored to the patient's symptoms and clinical diagnosis. To facilitate the diagnosis and treatment of sleep disorders and to better understand the neuropathological mechanisms of this sleep disorder, this review summarizes current knowledge on narcolepsy, in particular, genetic and non-genetic associations of narcolepsy, the pathophysiology up to the inflammatory response, the neuromorphological hallmarks of narcolepsy, and possible links with other diseases, such as diabetes, ischemic stroke and Alzheimer's disease. This review also reports all of the most recent updated research and therapeutic advances in narcolepsy. There have been significant advances in highlighting the pathogenesis of narcolepsy, with substantial evidence for an autoimmune response against hypocretin neurons; however, there are some gaps that need to be filled. To treat narcolepsy, more research should be focused on identifying molecular targets and novel autoantigens. In addition to therapeutic advances, standardized criteria for narcolepsy and diagnostic measures are widely accepted, but they may be reviewed and updated in the future with comprehension. Tailored treatment to the patient's symptoms and clinical diagnosis and future treatment modalities with hypocretin agonists, GABA agonists, histamine receptor antagonists and immunomodulatory drugs should be aimed at addressing the underlying cause of narcolepsy.

Modulation of sleep behavior in zebrafish larvae by pharmacological targeting of the orexin receptor

New pharmacological approaches that target orexin receptors (OXRs) are being developed to treat sleep disorders such as insomnia and narcolepsy, with fewer side effects than existing treatments. Orexins are neuropeptides that exert excitatory effects on postsynaptic neurons via the OXRs, and are important in regulating sleep/wake states. To date, there are three FDA-approved dual orexin receptor antagonists for the treatment of insomnia, and several small molecule oral OX2R (OXR type 2) agonists are in the pipeline for addressing the orexin deficiency in narcolepsy. To find new hypnotics and psychostimulants, rodents have been the model of choice, but they are costly and have substantially different sleep patterns to humans. As an alternative model, zebrafish larvae that like humans are diurnal and show peak daytime activity and rest at night offer several potential advantages including the ability for high throughput screening. To pharmacologically validate the use of a zebrafish model in the discovery of new compounds, we aimed in this study to evaluate the functionality of a set of known small molecule OX2R agonists and antagonists on human and zebrafish OXRs and to probe their effects on the behavior of zebrafish larvae. To this end, we developed an in vitro IP-One Homogeneous Time Resolved Fluorescence (HTRF) immunoassay, and in vivo locomotor assays that record the locomotor activity of zebrafish larvae under physiological light conditions as well as under dark-light triggers. We demonstrate that the functional IP-One test is a good predictor of biological activity in vivo. Moreover, the behavioral data show that a high-throughput assay that records the locomotor activity of zebrafish throughout the evening, night and morning is able to distinguish between OXR agonists and antagonists active on the zebrafish OXR. Conversely, a locomotor assay with alternating 30 min dark-light transitions throughout the day is not able to distinguish between the two sets of compounds, indicating the importance of circadian rhythm to their pharmacological activity. Overall, the results show that a functional IP-one test in combination with a behavioral assay using zebrafish is well-suited as a discovery platform to find novel compounds that target OXRs for the treatment of sleep disorders.

Characterization of T cell receptors reactive to HCRTNH2, pHA273-287, and NP17-31 in control and narcolepsy patients

Narcolepsy type 1 (NT1), a disorder caused by hypocretin/orexin (HCRT) cell loss, is associated with human leukocyte antigen (HLA)-DQ0602 (98%) and T cell receptor (TCR) polymorphisms. Increased CD4⁺ T cell reactivity to HCRT, especially DQ0602-presented amidated C-terminal HCRT (HCRT_NH2), has been reported, and homology with pHA_273-287 flu antigens from pandemic 2009 H1N1, an established trigger of the disease, suggests molecular mimicry. In this work, we extended DQ0602 tetramer and dextramer data to 77 cases and 44 controls, replicating our prior finding and testing 709 TCRs in Jurkat 76 T cells for functional activation. We found that fewer TCRs isolated with HCRT_NH2 (∼11%) versus pHA_273-287 or NP_17-31 antigens (∼50%) were activated by their ligand. Single-cell characterization did not reveal phenotype differences in influenza versus HCRT_NH2-reactive T cells, and analysis of TCR CDR3αβ sequences showed TCR clustering by responses to antigens but no cross-peptide class reactivity. Our results do not support the existence of molecular mimicry between HCRT and pHA_273-287 or NP_17-31.

Pediatric Narcolepsy—A Practical Review

Pediatric narcolepsy is a chronic sleep-wakefulness disorder. Its symptoms frequently begin in childhood. This review article examined the literature for research reporting on the effects of treatment of pediatric narcolepsy, as well as proposed etiology and diagnostic tools. Symptoms of pediatric narcolepsy include excessive sleepiness and cataplexy. In addition, rapid-eye-movement-related phenomena such as sleep paralysis, sleep terror, and hypnagogic or hypnapompic hallucinations can also occur. These symptoms impaired children’s function and negatively influenced their social interaction, studying, quality of life, and may further lead to emotional and behavioral problems. Therefore, early diagnosis and intervention are essential for children’s development. Moreover, there are differences in clinical experiences between Asian and Western population. The treatment of pediatric narcolepsy should be comprehensive. In this article, we review pediatric narcolepsy and its treatment approach: medication, behavioral modification, and education/mental support. Pharmacological treatment including some promising newly-developed medication can decrease cataplexy and daytime sleepiness in children with narcolepsy. Other forms of management such as psychosocial interventions involve close cooperation between children, school, family, medical personnel, and can further assist their adjustment.

Characterization of rapid weight gain phenotype in children with narcolepsy

Objectives

To characterize the rapid weight gain (RWG) phenotype associated with the onset of childhood narcolepsy and to determine whether it could constitute a marker of severity of the disease.

Methods

RWG was defined using the BMI z‐score slope reported to one year (>0.67 SD) from symptom onset to disease diagnosis. We compared the clinical, metabolic, and sleep characteristics between patients with or without RWG at diagnosis. Pharmacological management, anthropometric, and clinical progression were also evaluated during the follow‐up.

Results

A total of 84 de novo narcoleptic pediatric patients were included; their median age at diagnosis was 12.0 years; 59.5% boys, 90.5% cataplexy, and 98.7% HLA‐DQB1*06:02, 57% had RWG profile. RWG patients were younger at diagnosis than non‐RWG patients, despite a shorter diagnostic delay. They had a higher BMI z‐score and a higher prevalence of obesity at diagnosis, but not at symptom onset, and higher adapted Epworth Sleepiness Scale and Insomnia Severity Index scores than non‐RWG patients. No differences on nocturnal polysomnography and multiple sleep latency tests were found between groups at disease diagnosis. After a median follow‐up of 5 years, RWG patients still had a higher BMI z‐score and a higher prevalence of obesity despite benefiting from the same therapeutic management and displaying improvement in sleepiness and school difficulties.

Conclusions

Narcoleptic RWG patients were younger, sleepier, and the prevalence of obesity was higher at diagnosis despite a shorter diagnostic delay than that of non‐RWG patients. These patients had also a higher risk of developing a long‐term obesity, despite a positive progression of their narcoleptic symptoms. RGW could then represent a maker of a more severe phenotype of childhood narcolepsy, which should inspire a prompt and more offensive management to prevent obesity and its complications.

Narcolepsy among first- and second-generation immigrants in Sweden: A study of the total population

Aims

To study incident narcolepsy in first‐ and second‐generation immigrant groups using Swedish‐born individuals and native Swedes as referents.

Methods

The study population included all individuals registered and alive in Sweden at baseline. Narcolepsy was defined as having at least one registered diagnosis of narcolepsy in the Swedish National Patient Register. The incidence of narcolepsy in different immigrant groups was assessed by Cox regression, with hazard ratios (HRs) and 95% confidence intervals (CI). The models were stratified by sex and adjusted for age, geographical residence in Sweden, educational level, marital status, co‐morbidities, and neighbourhood socioeconomic status.

Results

In the first‐generation study, 1225 narcolepsy cases were found; 465 males and 760 females, and in the second‐generation study, 1710 cases, 702 males and 1008 females. Fully adjusted HRs (95% CI) in the first‐generation study was for males 0.83 (0.61–1.13) and females 0.83 (0.64–1.07), and in the second‐generation study for males 0.76 (0.60–0.95) and females 0.91 (95% CI 0.76–1.09). Statistically significant excess risks of narcolepsy were found in first‐generation males from North America, and second‐generation males with parents from North America, and second‐generation females with parents from Latin America.

Conclusions

There were only significant differences in incident narcolepsy between native Swedes and second‐generation male immigrants. The observed differences can partly be explained by differences in Pandemrix® vaccinations and are probably not attributable to genetic differences between immigrants and natives.

Association of HLA-DM and HLA class II Genes with Antibody Response Induced by Inactivated Japanese Encephalitis Vaccine

HLA (HLA) class II molecules, HLA-DR, DP, and DQ, together with HLA II-like protein DM, play a dominant role in the processing and presentation of antigens, which may influence vaccine effectiveness. We previously demonstrated that variations in the HLA-DRB1, DPB1, and DQB1 genes may affect the neutralising antibody (NAb) response induced by the inactivated Japanese encephalitis vaccine (IJEV). In the present study, we genotyped HLA-DPA1, DQA1, DMA, and DMB genes and used previous HLA-DRB1, DPB1, and DQB1 data to evaluate the association of these genes with IJEV-induced NAbs, at both the seroconversion and geometric mean titres (GMTs). We confirmed the seropositive association of DQB1*02:01 and NAbs (0.156 vs. 0.075, Padj = 0.018; OR = 2.270; 95% CI = 1.285-3.999) and seronegative association of DQB1*02:02 (0.014 vs. 0.09, Padj = 0.0002; OR = 0.130; 95% CI = 0.047-0.400). Furthermore, the DMB*01:03-DMA*01:01-DPA1*01:03-DPB1*04:01 haplotype was associated with a negative response (0.020 vs. 0.074; Padj = 0.03; OR = 0.250; 95% CI = 0.097-0.649), whereas DRB1*15:02-DMB*01:01-DMA*01:01 was associated with a positive response (0.034 vs. 0; Padj = 0.044). In addition, DRB1*12:02, DRB1*13:02, DPB1*04:01, DPB1*05:01, DPB1*09:01, DQA1*06:01, and DQA1*01:02 were associated with a higher GMT of NAbs, whereas DRB1*11:01, DPB1*13:01, and DQA1*05:05 were associated with a lower GMT of NAbs. In conclusion, the present study suggests that variations in the HLA-DM and HLA class II genes, as well as their combined allotypes, may influence the IJEV NAbs at seroconversion and GMT levels. This article is protected by copyright. All rights reserved.

Narcolepsia na Infância: A Atuação Multidisciplinar com a Psicologia do Sono do Diagnóstico ao Tratamento em um Relato de Caso

Resumo A narcolepsia, distúrbio neurológico crônico caracterizado pela sonolência diurna excessiva, pode ser associada à cataplexia, fragmentação do sono, alucinações relacionadas ao sono e paralisia do sono. Frequentemente, é confundida com outros transtornos, como Transtorno do Déficit de Atenção com Hiperatividade (TDAH), epilepsia e até esquizofrenia, assim, por vezes, é diagnosticada inadequadamente. Objetiva-se relatar o diagnóstico diferencial bem-sucedido da narcolepsia na infância e suas dificuldades, realizado por uma equipe multidisciplinar, enfocando a atuação da psicologia do sono em avaliação e intervenção. Um menino de 10 anos foi recebido no Ambulatório de Narcolepsia e Apneia do Sono Infantil (AMBNAP), alocado no Hospital Universitário Onofre Lopes da Universidade Federal do Rio Grande do Norte (UFRN) com queixas de sonolência diurna excessiva, sono fragmentado e episódios de perda de tônus muscular. Foi submetido a entrevistas psiquiátrica e psicológica pormenorizadas, a exames, aplicação de escalas específicas para rastreio e diagnóstico de transtornos de sono e diário de sono, solicitação de recursos de mídia e de relatório escolar e avaliação neurológica. A partir da investigação multidisciplinar, o diagnóstico foi de Narcolepsia e Síndrome da Apneia Obstrutiva do Sono (SAOS). O paciente foi submetido a técnicas da Terapia Cognitivo-Comportamental (TCC) e segue em acompanhamento, apresentando resultados satisfatórios. Este estudo evidencia que uma equipe multidisciplinar especializada na área de sono atuando em conjunto com a Psicologia do Sono oportuniza o diagnóstico e intervenções precoces eficazes para o tratamento do distúrbio do sono na infância.

Efficacy of Pitolisant on the Treatment of Narcolepsy: A Systematic Review

Narcolepsy is characterized by excessive daytime sleepiness (EDS) and cataplexy. Histamine neurons play an important role in enhancing wakefulness. The objective of our study was to evaluate the efficacy of pitolisant, a histamine 3 (H3)-receptor antagonist/inverse agonist, in patients with a high burden of narcolepsy symptoms. We conducted an advanced PubMed search strategy with inclusion and exclusion criteria. The outcome included the Epworth Sleepiness Scale (ESS) and adverse effects frequency. Our primary outcome included the mean ESS score at the endpoint and showed that pitolisant was superior to the placebo, but not non-inferior to modafinil. Adverse effects were less common and shorter in duration in the pitolisant group compared to the modafinil-treated patients. Pitolisant was efficacious in reducing excessive daytime sleepiness and cataplexy compared with placebo, and it was well-tolerated in patients with severe narcolepsy symptoms as compared with modafinil.

Reviewing the Clinical Implications of Treating Narcolepsy as an Autoimmune Disorder

Narcolepsy type 1 (NT1) is a lifelong sleep disorder, primarily characterized clinically by excessive daytime sleepiness and cataplexy and pathologically by the loss of hypocretinergic neurons in the lateral hypothalamus. Despite being a rare disorder, the NT1-related burden for patients and society is relevant due to the early onset and chronic nature of this condition. Although the etiology of narcolepsy is still unknown, mounting evidence supports a central role of autoimmunity. To date, no cure is available for this disorder and current treatment is symptomatic. Based on the hypothesis of the autoimmune etiology of this disease, immunotherapy could possibly represent a valid therapeutic option. However, contrasting and limited results have been provided so far. This review discusses the evidence supporting the use of immunotherapy in narcolepsy, the outcomes obtained so far, current issues and future directions.

A practical guide to the pharmacological and behavioral therapy of Narcolepsy

Narcolepsy is a rare, chronic, and disabling central nervous system hypersomnia; two forms can be recognized: narcolepsy type 1 (NT1) and narcolepsy type 2 (NT2). Its etiology is still largely unknown, but studies have reported a strong association between NT1 and HLA, as well as a pathogenic association with the deficiency of cerebrospinal hypocretin-1. Thus, the most reliable pathogenic hypothesis is an autoimmune process destroying hypothalamic hypocretin-producing cells. A definitive cure for narcolepsy is not available to date, and although the research in the field is highly promising, up to now, current treatments have aimed to reduce the symptoms by means of different pharmacological approaches. Moreover, overall narcolepsy symptoms management can also benefit from non-pharmacological approaches such as cognitive behavioral therapies (CBTs) and psychosocial interventions to improve the patients' quality of life in both adult and pediatric-affected individuals as well as the well-being of their families. In this review, we summarize the available therapeutic options for narcolepsy, including the pharmacological, behavioral, and psychosocial interventions.

Narcolepsy Presentation in Diverse Populations: an Update

Purpose of Review

We performed a literature search to generate incidence and prevalence rates of narcolepsy in diverse populations based on current available data.

Recent Findings

With an onset in childhood, narcolepsy often has a delayed diagnosis due to symptoms of excessive daytime sleepiness not being recognized or being misdiagnosed. Clinical, electrophysiological, and biological tests are needed in order to diagnose narcolepsy. At the same time, the discovery of the link with the immunoregulatory human leukocyte antigen complex and the adverse events in relation to the H1N1 pandemic vaccines have shuffled the epidemiological numbers.

Summary

In this meta-review, we pooled incidence rates and prevalence rates reported in 30 countries or from 209 sets of data. Findings are reported per age, continent, and proxy race/ethnicity as well as period (i.e., before/after the pandemic). This meta-review showed that narcolepsy occurs in 0.87–1.21 of the world population, with specifically NT1 being investigated. Its pooled incidence rate in vaccinated samples is 1.58. There is furthermore an underreporting of narcolepsy in ethnic/race and gender minorities, of childhood narcolepsy type 2 and potential comorbid conditions masking the clinical complaints and hence timely diagnosis.

Comorbidity of Narcolepsy and Psychotic Disorders: A Nationwide Population-Based Study in Taiwan

BACKGROUND

Narcolepsy is a chronic sleep disorder that is likely to have neuropsychiatric comorbidities. Psychotic disorders are characterized by delusion, hallucination, and reality impairments. This study investigates the relationship between narcolepsy and psychotic disorders.

DESIGN AND METHODS

This study involves patients who were diagnosed with narcolepsy between January 2002 and December 2011 (n = 258) and age- and gender-matched controls (n = 2580) from Taiwan's National Health Insurance database. Both the patients and the controls were monitored from January 1, 2002 to December 31, 2011 to identify any occurrence of a psychotic disorder. Drugs that have been approved for treating narcolepsy: immediate-release methylphenidate (IR-MPH), osmotic controlled-release formulations of methylphenidate (OROS-MPH), and modafinil, were analyzed. A multivariate logistic regression model was used to evaluate the potential comorbidity of narcolepsy with psychotic disorders.

RESULTS

During the study period, 8.1% of the narcoleptic patients exhibited comorbidity with a psychotic disorder, whereas only 1.5% of the control subjects (1.5%) had psychotic disorders (aOR, 4.07; 95% CI, 2.21-7.47). Of the narcolepsy patients, 41.5, 5.4, and 13.2% were treated with MPH-IR, MPH-OROS, and modafinil, accordingly. Pharmacotherapy for narcolepsy did not significantly affect the risk of exhibiting a psychotic disorder.

CONCLUSIONS

This nationwide study revealed that narcolepsy and psychotic disorders commonly co-occur. Pharmacotherapy for narcolepsy was not associated with the risk of psychotic disorders. Our findings serve as a reminder that clinicians must consider the comorbidity of narcolepsy and psychosis.

Narcolepsy in Children and Adults: A Guide to Improved Recognition, Diagnosis and Management

Narcolepsy is a rare condition that affects children and adults, and commonly has an onset in childhood. Time to appropriate diagnosis frequently is at least a decade. Unrecognized or misdiagnosed symptoms of narcolepsy contribute to increased morbidity, disability and socioeconomic liability in these patients. Delays in diagnosis may be related to variability in presentation in childhood, lack of familiarity with symptoms or appropriate diagnostic testing or misdiagnosis with accidental introduction of treatment that may modify or mask narcolepsy features. Improved awareness about the diagnosis and tailored therapies improve clinical and socioeconomic outcomes by reducing time to effective treatment. Application of effective treatment results in long-term benefits by improving clinical outcomes, potentially enabling improved education, increased employment opportunity, and improved work productivity and quality of life. This review provides a comprehensive stepwise approach to improve knowledge and comfort for recognition of symptoms, diagnostic strategies and management considerations of narcolepsy in children and adults.

Narcolepsy treatment: pharmacological and behavioral strategies in adults and children

Narcolepsy is a disabling, rare, and chronic sleep disorder, currently classified as distinct central nervous system hypersomnia in narcolepsy type 1 (NT1) and narcolepsy type 2 (NT2). Although today a reliable pathogenic hypothesis identifies the cause of NT1 as an autoimmune process destroying hypocretin-producing cells, there is no cure for narcolepsy, and the symptomatic pharmacological available treatments are not entirely effective for all symptoms. Behavioral therapies play a synergistic role in the disease treatment. We here review the available therapeutic options for narcolepsy, including symptomatic pharmacological treatments as well as behavioral and psychosocial interventions that could help clinicians improve the quality of life of patients with narcolepsy in adulthood and childhood.

Autoimmunity to hypocretin and molecular mimicry to flu in type 1 narcolepsy

This work shows that the amidated terminal ends of the secreted hypocretin (HCRT) peptides (HCRT_NH2) are autoantigens in type 1 narcolepsy, an autoimmune disorder targeting HCRT neurons. The autoimmune process is usually initiated by influenza A flu infections, and a particular piece of the hemagglutinin (HA) flu protein of the pandemic 2009 H1N1 strain was identified as a likely trigger. This HA epitope has homology with HCRT_NH2 and T cells cross-reactive to both epitopes are involved in the autoimmune process by molecular mimicry. Genes associated with narcolepsy mark the particular HLA heterodimer (DQ0602) involved in presentation of these antigens and modulate expression of the specific T cell receptor segments (TRAJ24 and TRBV4-2) involved in T cell receptor recognition of these antigens, suggesting causality.

Type 1 narcolepsy (T1N) is caused by hypocretin/orexin (HCRT) neuronal loss. Association with the HLA DQB1*06:02/DQA1*01:02 (98% vs. 25%) heterodimer (DQ0602), T cell receptors (TCR) and other immune loci suggest autoimmunity but autoantigens are unknown. Onset is seasonal and associated with influenza A, notably pandemic 2009 H1N1 (pH1N1) infection and vaccination (Pandemrix). Peptides derived from HCRT and influenza A, including pH1N1, were screened for DQ0602 binding and presence of cognate DQ0602 tetramer-peptide–specific CD4⁺ T cells tested in 35 T1N cases and 22 DQ0602 controls. Higher reactivity to influenza pHA_273–287 (pH1N1 specific), PR8 (H1N1 pre-2009 and H2N2)-specific NP_17–31 and C-amidated but not native version of HCRT_54–66 and HCRT_86–97 (HCRT_NH2) were observed in T1N. Single-cell TCR sequencing revealed sharing of CDR3β TRBV4-2-CASSQETQGRNYGYTF in HCRT_NH2 and pHA_273–287-tetramers, suggesting molecular mimicry. This public CDR3β uses TRBV4-2, a segment modulated by T1N-associated SNP rs1008599, suggesting causality. TCR-α/β CDR3 motifs of HCRT_54–66-NH2 and HCRT_86–97-NH2 tetramers were extensively shared: notably public CDR3α, TRAV2-CAVETDSWGKLQF-TRAJ24, that uses TRAJ24, a chain modulated by T1N-associated SNPs rs1154155 and rs1483979. TCR-α/β CDR3 sequences found in pHA_273–287, NP_17–31, and HCRT_NH2 tetramer-positive CD4⁺ cells were also retrieved in single INF-γ–secreting CD4⁺ sorted cells stimulated with Pandemrix, independently confirming these results. Our results provide evidence for autoimmunity and molecular mimicry with flu antigens modulated by genetic components in the pathophysiology of T1N.

Sleep disorders during childhood: a practical review

Sleep disorders are a common problem during childhood. The consequences are variable, and sleep disorders can influence medical, psychological and developmental aspects of the growing child. It is important to recognize sleep disorders and to treat them correctly. We discuss common sleep disorders during childhood using the 3rd edition of the International Classification of Sleep Disorders. We analyze the different sleep disorders from a clinical approach and provide an overview of adequate treatment options.Conlusion: This review discusses common sleep disorders during childhood using the 3rd edition of the International Classification of Sleep Disorders. We analyze the different sleep disorders from a clinical approach and provide an overview of adequate treatment options. What is known: • Sleep disorders are a common problem during childhood. • The consequences are variable, and sleep disorders can influence medical, psychological, and developmental aspects of the growing child. What is new: • Pediatricians should routinely screen for sleep and sleep disorders. • It is important to recognize sleep disorders and to treat them correctly.

Absence of anti-hypocretin receptor 2 autoantibodies in post pandemrix narcolepsy cases

Background

A recent publication suggested molecular mimicry of a nucleoprotein (NP) sequence from A/Puerto Rico/8/1934 (PR8) strain, the backbone used in the construction of the reassortant strain X-179A that was used in Pandemrix^® vaccine, and reported on anti-hypocretin (HCRT) receptor 2 (anti-HCRTR2) autoantibodies in narcolepsy, mostly in post Pandemrix^® narcolepsy cases (17 of 20 sera). In this study, we re-examined this hypothesis through mass spectrometry (MS) characterization of Pandemrix^®, and two other pandemic H1N1 (pH1N1)-2009 vaccines, Arepanrix^® and Focetria^®, and analyzed anti-HCRTR2 autoantibodies in narcolepsy patients and controls using three independent strategies.

Methods

MS characterization of Pandemrix^® (2 batches), Arepanrix^® (4 batches) and Focetria^® (1 batch) was conducted with mapping of NP 116I or 116M spectrogram. Two sets of narcolepsy cases and controls were used: 40 post Pandemrix^® narcolepsy (PP-N) cases and 18 age-matched post Pandemrix^® controls (PP-C), and 48 recent (≤6 months) early onset narcolepsy (EO-N) cases and 70 age-matched other controls (O-C). Anti-HCRTR2 autoantibodies were detected using three strategies: (1) Human embryonic kidney (HEK) 293T cells with transient expression of HCRTR2 were stained with human sera and then analyzed by flow cytometer; (2) In vitro translation of [³⁵S]-radiolabelled HCRTR2 was incubated with human sera and immune complexes of autoantibody and [³⁵S]-radiolabelled HCRTR2 were quantified using a radioligand-binding assay; (3) Optical density (OD) at 450 nm (OD450) of human serum immunoglobulin G (IgG) binding to HCRTR2 stably expressed in Chinese hamster ovary (CHO)-K1 cell line was measured using an in-cell enzyme-linked immunosorbent assay (ELISA).

Results

NP 116M mutations were predominantly present in all batches of Pandemrix^®, Arepanrix^® and Focetria^®. The wild-type NP_109-123 (ILYDKEEIRRIWRQA), a mimic to HCRTR2_34-45 (YDDEEFLRYLWR), was not found to bind to DQ0602. Three or four subjects were found positive for anti-HCRTR2 autoantibodies using two strategies or the third one, respectively. None of the post Pandemrix^® narcolepsy cases (0 of 40 sera) was found positive with all three strategies.

Conclusion

Anti-HCRTR2 autoantibody is not a significant biological feature of narcolepsy or of post Pandemrix^® autoimmune responses.