Response to immunotherapy in anti-IgLON5 disease: A systematic review

Anti-IgLON5 disease: A case with intestinal obstruction and peripheral neuropathy

IgLON5 autoimmunity is a novel antibody-mediated disorder characterized by serum and/or cerebrospinal fluid (CSF) positivity for IgLON5 antibody. Anti-IgLON5 disease mainly manifests as sleep disturbances, movement disorders and brainstem syndromes. In this study, we report the case of a patient with anti-IgLON5 disease who presented with abdominal distension, abdominal pain, intermittent dysuria and constipation, and intermittent lightning pain in the extremities, which are atypical of anti-IgLON5 disease and could easily lead to misdiagnosis. After performing autoantibody screening, we considered anti-IgLON5 disease. The patient was started on a course of immunotherapy with intravenous dexamethasone, intravenous immunoglobulin (IVIG) and oral azathioprine. Following treatment, the manifestations nearly resolved. The clinical manifestations of anti-IgLON5 disease are diverse and may present in different combinations, which can easily lead to misdiagnosis. Early recognition and treatment of this autoimmune disease with immunosuppressive agents may lead to better outcomes.

Anti-IgLON5 Disease Showing an Improvement in Dysautonomia, Including Vocal Cord Palsy, via Combined Immunotherapy

Anti-IgLON5 disease shows various neurological manifestations, of which dysautonomia is one of the major symptoms and is rarely improved by immunotherapy. We herein report a patient with anti-IgLON5 disease who showed several autonomic failures, including vocal cord palsy for four months. The patient presented with cognitive impairments, bulbar symptoms accompanied by myorhythmia in the pharynx and tongue, cerebellar ataxia with tremor, motor neuron symptoms in the limbs, gastrointestinal dysfunction, orthostatic hypotension, non-rapid eye movement sleep disorder on polysomnography, and severe vocal cord palsy. Combined immunotherapy improved his symptoms, including vocal cord palsy, suggesting that combined immunotherapy might improve dysautonomia in anti-IgLON5 disease.

IgLON5-IgG: Innocent Bystander or Perpetrator?

Anti-IgLON5 (IgLON5-IgG)-associated disease is a newly defined clinical entity. This literature review aims to evaluate its pathogenesis, which remains a pivotal question. Features that favour a primary neurodegenerative mechanism include the non-inflammatory tauopathy neuropathological signature and overrepresentation of microtubule-associated protein tau (MAPT) H1/H1 genotype as seen in other sporadic tauopathies. In contrast, the cell-surface localisation of IgLON5, capability of anti-IgLON5 antibodies to exert direct in vitro pathogenicity and disrupt IgLON5 interactions with its binding partners, human leukocyte antigen (HLA)-DRB1*10:01 and HLA-DQB1*05:01 allele preponderance with high affinity binding of IgLON5 peptides, and responsiveness to immunotherapy favour a primary autoimmune process. The presentation and course of anti-IgLON5-associated disease is heterogenous; hence, we hypothesise that a multitude of immune mechanisms are likely simultaneously operational in this disease cohort.

A rare pediatric patient of anti-IgLON5 encephalitis with epileptic seizures as the first symptom

BACKGROUND

Anti-IgLON5 encephalitis was a rare neurological and heterogeneous disorder, which was mainly found in adults. Epileptic seizures related to anti-IgLON5 disease were rarely reported.

METHODS

Neural antibodies associated with autoimmune encephalitis in serum and cerebrospinal fluid (CSF) were tested using cell-based assays (CBA) with immunofluorescence double staining. The antibodies in serum were further confirmed by tissue-based assay (TBA) with rat brain and kidney tissue.

RESULTS

We reported a pediatric case presented with epileptic seizures, cognitive impairments, and sleep disorders. Autoantibody screening showed anti-IgLON5 antibody IgG (1:100+) and anti-NMDAR antibody IgG (1:10+) in the serum. She was diagnosed as anti-IgLON5 encephalitis. Her conditions improved rapidly by treated with intravenous immunoglobulin and high dose intravenous methylprednisolone.

CONCLUSION

We described the second pediatric case with anti-IgLON5 encephalitis, who was also the first presented with epileptic seizures as the initial presentation. Anti-IgLON5 encephalitis might have mild manifestations. For patients with new onset seizures associated with cognitive impairments and sleep disturbances, anti-IgLON5 antibody should be tested as early, even in children.

HLA-DQB1*05 subtypes and not DRB1*10:01 mediates risk in anti-IgLON5 disease

Anti-IgLON5 disease is a rare and likely underdiagnosed subtype of autoimmune encephalitis. The disease displays a heterogeneous phenotype that includes sleep, movement and bulbar-associated dysfunction. The presence of IgLON5-antibodies in CSF/serum, together with a strong association with HLA-DRB1*10:01∼DQB1*05:01, supports an autoimmune basis. In this study, a multicentric human leukocyte antigen (HLA) study of 87 anti-IgLON5 patients revealed a stronger association with HLA-DQ than HLA-DR. Specifically, we identified a predisposing rank-wise association with HLA-DQA1*01:05∼DQB1*05:01, HLA-DQA1*01:01∼DQB1*05:01 and HLA-DQA1*01:04∼DQB1*05:03 in 85% of patients. HLA sequences and binding cores for these three DQ heterodimers were similar, unlike those of linked DRB1 alleles, supporting a causal link to HLA-DQ. This association was further reflected in an increasingly later age of onset across each genotype group, with a delay of up to 11 years, while HLA-DQ-dosage dependent effects were also suggested by reduced risk in the presence of non-predisposing DQ1 alleles. The functional relevance of the observed HLA-DQ molecules was studied with competition binding assays. These proof-of-concept experiments revealed preferential binding of IgLON5 in a post-translationally modified, but not native, state to all three risk-associated HLA-DQ receptors. Further, a deamidated peptide from the Ig2-domain of IgLON5 activated T cells in two patients, compared with one control carrying HLA-DQA1*01:05∼DQB1*05:01. Taken together, these data support a HLA-DQ-mediated T-cell response to IgLON5 as a potentially key step in the initiation of autoimmunity in this disease.

Atypical brain MRI findings in a patient with treatment responsive anti-IgLON5 disease

Anti-IgLON5 disease is a rare autoimmune neurological condition which was relatively recently described in the literature. This syndrome encompasses a range of clinical manifestations with most cases showing unremarkable findings on brain magnetic resonance imaging (MRI). Here, we report a case of a 61-year-old female patient with unique brain MRI features that, to the best of our knowledge, has not been reported in the literature before. Following treatment including immunotherapy, the patient experienced significant improvement clinically accompanied by radiological improvement on the follow-up imaging.

Recent advances in non-Huntington's disease choreas

INTRODUCTION

Chorea is primarily due to an imbalance of basal ganglia output pathways, often due to dysfunction or degeneration of the caudate nucleus and putamen, and can be due to many causes.

METHODS

We reviewed the recent literature to identify newly-recognized causes of chorea, including auto-immune, metabolic, and genetic. We also focused upon developments in mechanisms relating to underlying pathophysiology of certain genetic choreas and advances in therapeutics.

RESULTS

Novel autoantibodies continue to be identified as causes of chorea. Both COVID-19 infection and vaccination are reported to result rarely in chorea, although in some cases causality is not clearly established. Advances in genetic testing continue to find more causes of chorea, and to expand the phenotype of known genetic disorders. Deep brain stimulation can be successful in certain circumstances.

CONCLUSION

Our understanding of mechanisms underlying this movement disorder continues to advance, however much remains to be elucidated.

Differentiating anti-IgLON5 disease and Lewy body dementia: a systematic review

BACKGROUND

Anti-IgLON5 disease is a rare but potentially reversible cause of cognitive impairment, sleep disturbances, dysautonomia, and movement disorders. It is an autoimmune encephalitis which, due to its insidious onset, could mimic neurodegenerative disorders, and multiple symptoms overlap with those seen in dementia with Lewy bodies (DLB). We hypothesized that the symptomatology and findings in patients with anti-IgLON5 disease overlapped with that of DLB.

OBJECTIVES

To assess the commonality of features in anti-IgLON5 disease and DLB and identify potential red flags for anti-IgLON5 disease in patients undergoing diagnostic evaluation for DLB.

METHODS

We searched in MEDLINE, Web of Science, and Embase from inception on December the 8th, 2022 with the search term "IgLON5". We performed a systematic review of case reports and case series of anti-IgLON5 disease, and two reviewers independently extracted data on symptoms and findings. Frequencies of symptoms were compared with consensus criteria for DLB.

RESULTS

We included 57 studies with 127 individual case reports of anti-IgLON5 disease (mean age 63 years at diagnosis, median symptom duration 2 years). Cognitive dysfunction was reported in 45% of cases, REM-sleep behavioral disorder in 15%, and 14% had parkinsonism. Respiratory insufficiency was reported in 37%, and bulbar symptoms in 67%.

CONCLUSIONS

We found a significant overlap between anti-IgLON5 disease and DLB. We propose that anti-IgLON5 disease should be considered in young patients with DLB with chorea, gaze palsy, early dysphagia, or prominent respiratory symptoms. Our study contributes to the emerging knowledge on symptoms and biomarkers in anti-IgLON5 disease.

Coexistence of anti-NMDAR and anti-IgLON5 antibodies in an autoimmune encephalitis patient: The first case report

Background

The coexistence of autoimmune encephalitis (AE) with multiple neural auto-antibodies is of great clinical significance because overlying antibodies may cause superposition or variation of clinical syndrome, which increases the difficulty of diagnosis and treatment of the disease. To the best of our knowledge, the coexistence of anti-N-methyl d-aspartate Receptor (NMDAR) and anti-IgLON5 antibodies in AE has not been published previously.

Case presentation

A 38-year-old female patient presented to our hospital due to headache and abnormal psychiatric behavior. Based on her clinical manifestations (psychiatric and behavioral abnormalities, involuntary limb movements, and sleep disorders) and laboratory assessment results (positive human leukocyte antigen (HLA)-DQB1*05:01 haplotype, anti-NMDAR, and anti-IgLON5 antibodies), she was diagnosed as AE with coexisting anti-NMDAR and anti-IgLON5 antibodies. After treatment with intravenous methylprednisolone and immunoglobulin, as well as plasmapheresis, her symptoms gradually improved with exception for the sleep disorders. Although oral prednisone acetate and mycophenolate mofetil were continued after discharge, her symptoms of sleep disorders did not improve at 6-month follow-up.

Conclusion

This is the first case of AE co-existing with anti-NMDAR and anti-IgLON5 antibodies. Co-existence of neural auto-antibodies should be considered when patients present with overlapping or atypical symptoms. Special attention should be paid to the treatment of these patients as some anti-IgLON5 encephalitis patients may not benefit from immunotherapy treatment.

Atypical neurological manifestations in anti-IgLON5 disease: a case report

Anti-IgLON5 disease is a recently discovered autoimmune encephalopathy with sleep disorder as a hallmark in the majority of reported cases. Additional neurological manifestations include bulbar dysfunction, gait problems, movement disorders, oculomotor abnormalities, and hyperexcitability of the nervous system. At present, an increasing number of publications have dealt with the course and possible treatment options for anti-IgLON5 disease, and its clinical spectrum has expanded wider and more heterogeneous. Here, we report a case of a 66-year-old female with cognitive impairment accompanied by slow reaction, impaired memory, and decreased orientation. A positive cerebral MRI change and serum and cerebrospinal fluid (CSF) antibodies against IgLON5 were found during the diagnostic course. Subsequently the patient received immunotherapy and was generally in good health with no new symptoms during follow-up. Early testing for IgLON5 antibodies should be considered in patients with atypical neurological symptoms such as cognitive impairment, slow reaction, or decreased orientation. In clinical practice, immunotherapy should be considered in all cases of anti-IgLON5 encephalopathies.

The psychiatric symptoms in anti-IgLON5 disease: Case report and literature review

Immunotherapy may be ineffective in the advanced stages of anti-IgLON5 disease with psychiatric symptoms. The psychiatric symptoms in advanced stages of anti-IgLON5 disease may be associated with neurodegeneration.

PSP-Richardson syndrome mimics: An overview and pragmatic approach

Progressive supranuclear palsy-Richardson syndrome (PSP-RS) is a sporadic atypical parkinsonian syndrome with levodopa-unresponsive axial-predominant parkinsonism, early postural instability, vertical supranuclear gaze palsy, dysarthria, executive dysfunction and behavioural changes. PSP-RS can be mimicked by numbers of other disorders, generally known as PSP mimics, or PSP-like syndromes. Their aetiological spectrum includes neurodegenerative (mostly genetic), vascular, infectious and drug-induced illnesses as well as other causes. Based on the available data, we have tried to create a definition of PSP-RS mimics: a syndrome resembling PSP-RS with at least one of the following red flags: 1) positive family history; 2) onset before 45 years of age; 3) rapid or stepwise progression; 4) acute or subacute onset; 5) atypical symptoms and/or signs; 6) normal or atypical brain MRI; 7) history of HIV or untreated syphilis, aortal surgery or recent therapy with dopamine-blocking agents. We have suggested a short diagnostic algorithm leading to the identification of PSP-RS mimics and the recommended diagnostic work-up. The key point of the diagnostic process is the early identification and treatment of potentially treatable PSP-RS mimics.

SOCS-JAK-STAT inhibitors and SOCS mimetics as treatment options for autoimmune uveitis, psoriasis, lupus, and autoimmune encephalitis

Autoimmune diseases arise from atypical immune responses that attack self-tissue epitopes, and their development is intricately connected to the disruption of the JAK-STAT signaling pathway, where SOCS proteins play crucial roles. Conditions such as autoimmune uveitis, psoriasis, lupus, and autoimmune encephalitis exhibit immune system dysfunctions associated with JAK-STAT signaling dysregulation. Emerging therapeutic strategies utilize JAK-STAT inhibitors and SOCS mimetics to modulate immune responses and alleviate autoimmune manifestations. Although more research and clinical studies are required to assess their effectiveness, safety profiles, and potential for personalized therapeutic approaches in autoimmune conditions, JAK-STAT inhibitors and SOCS mimetics show promise as potential treatment options. This review explores the action, effectiveness, safety profiles, and future prospects of JAK inhibitors and SOCS mimetics as therapeutic agents for psoriasis, autoimmune uveitis, systemic lupus erythematosus, and autoimmune encephalitis. The findings underscore the importance of investigating these targeted therapies to advance treatment options for individuals suffering from autoimmune diseases.

Sleep Disturbances in Autoimmune Neurological Diseases

PURPOSE OF REVIEW

To summarize the current evidence on the associations between autoimmune neurological diseases (e.g., multiple sclerosis, myasthenia gravis) and sleep disturbances (e.g., insomnia, parasomnias), as well as to review the main characteristics of sleep disorders with an immune-related pathophysiology (e.g., narcolepsy, anti-IgLON5 disease).

RECENT FINDINGS

An immune-mediated damage of the areas in the central nervous system that control sleep and wake functions (e.g., hypothalamus, brainstem) can lead to sleep disorders and sleep symptoms. Sleep disturbances are the reason to seek for medical attention in certain neuroimmunological conditions (e.g., narcolepsy, anti-IgLON5 disease) where sleep-related alterations are the main clinical feature. The assessment of sleep-related symptomatology and disorders should be included in the routine evaluation of patients with autoimmune neurological diseases. Clinicians should be aware of the typical clinical presentation of certain neuroimmunological disorders mainly affecting sleep.

Immunotherapies in MuSK-positive Myasthenia Gravis; an IgG4 antibody-mediated disease

Muscle-specific kinase (MuSK) Myasthenia Gravis (MG) represents a prototypical antibody-mediated disease characterized by predominantly focal muscle weakness (neck, facial, and bulbar muscles) and fatigability. The pathogenic antibodies mostly belong to the immunoglobulin subclass (Ig)G4, a feature which attributes them their specific properties and pathogenic profile. On the other hand, acetylcholine receptor (AChR) MG, the most prevalent form of MG, is characterized by immunoglobulin (Ig)G1 and IgG3 antibodies to the AChR. IgG4 class autoantibodies are impotent to fix complement and only weakly bind Fc-receptors expressed on immune cells and exert their pathogenicity via interfering with the interaction between their targets and binding partners (e.g. between MuSK and LRP4). Cardinal differences between AChR and MuSK-MG are the thymus involvement (not prominent in MuSK-MG), the distinct HLA alleles, and core immunopathological patterns of pathology in neuromuscular junction, structure, and function. In MuSK-MG, classical treatment options are usually less effective (e.g. IVIG) with the need for prolonged and high doses of steroids difficult to be tapered to control symptoms. Exceptional clinical response to plasmapheresis and rituximab has been particularly observed in these patients. Reduction of antibody titers follows the clinical efficacy of anti-CD20 therapies, a feature implying the role of short-lived plasma cells (SLPB) in autoantibody production. Novel therapeutic monoclonal against B cells at different stages of their maturation (like plasmablasts), or against molecules involved in B cell activation, represent promising therapeutic targets. A revolution in autoantibody-mediated diseases is pharmacological interference with the neonatal Fc receptor, leading to a rapid reduction of circulating IgGs (including autoantibodies), an approach already suitable for AChR-MG and promising for MuSK-MG. New precision medicine approaches involve Chimeric autoantibody receptor T (CAAR-T) cells that are engineered to target antigen-specific B cells in MuSK-MG and represent a milestone in the development of targeted immunotherapies. This review aims to provide a detailed update on the pathomechanisms involved in MuSK-MG (cellular and humoral aberrations), fostering the understanding of the latest indications regarding the efficacy of different treatment strategies.

Origins and immunopathogenesis of autoimmune central nervous system disorders

The field of autoimmune neurology is rapidly evolving, and recent discoveries have advanced our understanding of disease aetiologies. In this article, we review the key pathogenic mechanisms underlying the development of CNS autoimmunity. First, we review non-modifiable risk factors, such as age, sex and ethnicity, as well as genetic factors such as monogenic variants, common variants in vulnerability genes and emerging HLA associations. Second, we highlight how interactions between environmental factors and epigenetics can modify disease onset and severity. Third, we review possible disease mechanisms underlying triggers that are associated with the loss of immune tolerance with consequent recognition of self-antigens; these triggers include infections, tumours and immune-checkpoint inhibitor therapies. Fourth, we outline how advances in our understanding of the anatomy of lymphatic drainage and neuroimmune interfaces are challenging long-held notions of CNS immune privilege, with direct relevance to CNS autoimmunity, and how disruption of B cell and T cell tolerance and the passage of immune cells between the peripheral and intrathecal compartments have key roles in initiating disease activity. Last, we consider novel therapeutic approaches based on our knowledge of the immunopathogenesis of autoimmune CNS disorders.

Anti-IgLON5 disease exacerbated by asymptomatic SARS-CoV-2 infection

Objective

To report a case of anti-IgLON5 disease unmasked by asymptomatic SARS-CoV-2 infection.

Background

Anti-IgLON5 disease is a clinically heterogeneous disease that shares features of both neurodegeneration and neuroinflammation. The onset can be insidious, posing diagnostic challenges and often resulting in treatment delay. Infectious trigger was rarely reported in this disease.

Case report

A 64-year-old male initially presented with 1-year history of progressive parasomnia and mild cognitive decline that precipitously worsened over the course of 1 month following asymptomatic SARS-CoV-2 infection, resulting in dysphagia, parkinsonism, weight loss and dependence on all activities of daily living. He was found to have high titer (1:3840) of anti-IgLON5 antibody in the serum, confirming the diagnosis of anti-IgLON5 disease.

Conclusion

Anti-IgLON5 disease as a potentially reversible cause of neurodegenerative syndrome in patients with atypical features. Timely diagnosis and treatment may improve clinical outcomes. It is also worth noting that symptoms precipitously worsened following SARS-CoV-2 infection. We suspect that a COVID-19-mediated immune activation response exacerbated the underlying autoimmune encephalitis process, unmasking his symptoms.

Anti-IgLON5 disease complicated with rectal adenocarcinoma: a case report

BACKGROUND

Anti-IgLON5 disease is a rare chronic autoimmune-mediated tauopathy, featured by the sleep disturbance. Several studies have described its clinical characteristics, however, the simultaneous occurrence of anti-IgLON5 disease and rectal cancer has not been reported. We described an unusual entity of anti-IgLON5 disease complicated with rectal cancer.

CASE PRESENTATION

A 76-year-old man initially presented with slurred speech and limb tremors, followed by epileptic-like seizures, lethargy, and sleep apnea. IgG anti-IgLON5 antibodies were positive in both serum and cerebrospinal fluid. The patient responded well to the treatment of plasma exchange and a pulse and gradual reduction of steroids therapy. When the oral steroids started, mycophenolate mofetil was added. Two months later, the patient had bloody stools and pathological-confirmed moderately differentiated adenocarcinoma of the rectum.

CONCLUSIONS

Whereas sleep disturbance is the most common feature in patients with anti-IgLON5 disease, our case presented with slurred speech and limb tremors. Anti-IgLON5 disease complicated with rectal cancer is very rare. Tumor screening should be considered in patients with anti-IgLON5 disease to investigate the association between tumor and this disease.

Epileptic seizures in patients with anti-IgLON5 disease

BACKGROUND

Anti-IgLON5 is a rare neurologic disease that can present with epileptic seizures. However, epileptic seizures have not been characterized and are underreported. We aimed to investigate the clinical characteristics and demographics of epileptic seizures in patients with anti-IgLON5 disease.

METHODS

We reported a case of anti-IgLON5 disease presenting with epileptic seizures and presented a comprehensive literature review on epileptic seizures in patients with the anti-IgLON5 disease. We searched the Medline, Pubmed, and Web of Science databases using the following search algorithm: "IgLON5" or "anti-IgLON5" or "IgLON5 antibody" limited to publications in English.

RESULTS

We identified 183 cases from 66 publications. In addition to our case, nine (4.9%) patients with anti-IgLON5 disease had reported epileptic seizures, either focal or generalized. Of those, epileptic seizures were one of the main reasons for neurology consultation in six (3.2%). Patients with epileptic seizures affected both sexes similarly and usually developed in middle age. In addition to epileptic seizures, a majority of patients had sleep disorders and cognitive impairment. The frequency of epileptic seizures was reduced with the treatment of immunotherapy and antiseizure medication.

CONCLUSION

Anti-IgLON5 disease can present with epileptic seizures, and our study expands the clinical spectrum of the anti-IgLON5 disease.

Anti-IgLON5 Disease with Isolated Hemichorea: A Case Report and Review of the Literature

Background

Anti-IgLON5 disease is an autoimmune encephalopathy with sleep disturbances as a hallmark in the majority of reported cases. Additional clinical symptoms are heterogenous and include movement disorders, bulbar dysfunction, autonomic disorders, and neurocognitive impairment.

Case

Here, we report the case of an 87-year-old woman presenting with isolated progressive hemichorea. An extensive diagnostic work-up revealed antibodies against IgLON5 in the serum. Neither history nor polysomnography (PSG) unveiled signs and features of sleep dysfunction typically reported in anti-IgLON5 disease.

Literature Review

In an extensive literature review we identified twelve other studies reporting about patients with confirmed anti-IgLON5 disease and chorea as extrapyramidal movement disorder in their clinical phenotype. Subsequently, clinical characteristics of these patients were carefully evaluated.

Conclusions

Our results support the diversity of clinical phenotypes in anti-IgLON5 disease, adding isolated hemichorea to the spectrum of presenting symptoms. As sleep-related disorders are often not the leading reason for consultation and only revealed by PSG examination, we suggest that screening for antibodies against IgLON5 should be considered in patients presenting with unexplained movement disorders, including isolated hemichorea.

Anti-IgLON5 disease: a novel topic beyond neuroimmunology

Anti-IgLON5 disease is a recently defined autoimmune disorder of the nervous system associated with autoantibodies against IgLON5. Given its broad clinical spectrum and extremely complex pathogenesis, as well as difficulties in its early diagnosis and treatment, anti-IgLON5 disease has become the subject of considerable research attention in the field of neuroimmunology. Anti-IgLON5 disease has characteristics of both autoimmunity and neurodegeneration due to the unique activity of the anti-IgLON5 antibody. Neuropathologic examination revealed the presence of a tauopathy preferentially affecting the hypothalamus and brainstem tegmentum, potentially broadening our understanding of tauopathies. In contrast to that seen with other autoimmune encephalitis-related antibodies, basic studies have demonstrated that IgLON5 antibody-induced neuronal damage and degeneration are irreversible, indicative of a potential link between autoimmunity and neurodegeneration in anti-IgLON5 disease. Herein, we comprehensively review and discuss basic and clinical studies relating to anti-IgLON5 disease to better understand this complicated disorder.

Who to Enroll in Parkinson Disease Prevention Trials? The Case for Composite Prodromal Cohorts

Significant progress has been made in expanding our understanding of prodromal Parkinson disease (PD), particularly for recognition of early motor and nonmotor signs and symptoms. Although identification of these prodromal features may improve our understanding of the earliest stages of PD, they are individually insufficient for early disease detection and enrollment of participants in prevention trials in most cases because of low sensitivity, specificity, and positive predictive value. Composite cohorts, composed of individuals with multiple co-occurring prodromal features, are an important resource for conducting prodromal PD research and eventual prevention trials because they are more representative of the population at risk for PD, allow investigators to evaluate the efficacy of an intervention across individuals with varying prodromal feature patterns, are able to produce larger sample sizes, and capture individuals at different stages of prodromal PD. A key challenge in identifying individuals with prodromal disease for composite cohorts and prevention trial participation is that we know little about the natural history of prodromal PD. To move toward prevention trials, it is critical that we better understand common prodromal feature patterns and be able to predict the probability of progression and phenoconversion. Ongoing research in cohort studies and administrative databases is beginning to address these questions, but further longitudinal analyses in a large population-based sample are necessary to provide a convincing and definitive strategy for identifying individuals to be enrolled in a prevention trial.

Clinical Reasoning: A 77-Year-Old Man With Involuntary Movements, Sleep Changes, Falls, Bulbar Symptoms, and Cognitive Complaints

A 77-year-old-man presents with chorea, parasomnias, dysarthria and dysphagia, and cognitive issues. A broad workup reveals positive anti-IgLON5 antibody. This case report represents a textbook example of anti-IgLON5 syndrome.

What Is the Prognostic Significance of Rapid Eye Movement Sleep Without Atonia in a Polysomnogram?

SUMMARY

Freud said we are lucky to be paralyzed during sleep, so we cannot act out our dreams. Atonia of skeletal muscles normally present during rapid eye movement sleep prevents us from acting out our dreams. Observing rapid eye movement sleep without atonia in a polysomnogram in older adults first and foremost warrants consideration of rapid eye movement behavior disorder. Seventy-five to 90% of older adults with isolated rapid eye movement behavior disorder will develop a neurodegenerative disease within 15 years, most often a synucleinopathy. Rapid eye movement sleep without atonia in those younger than 50 years is commonly found in individuals with narcolepsy and those taking antidepressant medications.

Immunotherapy in autoimmune encephalitis

PURPOSE OF REVIEW

Autoimmune encephalitis (AE) refers to immune-mediated neurological syndromes often characterised by the detection of pathogenic autoantibodies in serum and/or cerebrospinal fluid which target extracellular epitopes of neuroglial antigens. There is increasing evidence these autoantibodies directly modulate function of their antigens in vivo. Early treatment with immunotherapy improves outcomes. Yet, these patients commonly exhibit chronic disability. Importantly, optimal therapeutic strategies at onset and during escalation remain poorly understood. In this review of a rapidly emerging field, we evaluate recent studies on larger cohorts, registries, and meta-analyses to highlight existing evidence for contemporary therapeutic approaches in AE.

RECENT FINDINGS

We highlight acute and long-term treatments used in specific AE syndromes, exemplify how understanding disease pathogenesis can inform precision therapy and outline challenges of defining disability outcomes in AE.

SUMMARY

Early first-line immunotherapies, including corticosteroids and plasma exchange, improve outcomes, with emerging evidence showing second-line immunotherapies (especially rituximab) reduce relapse rates. Optimal timing of immunotherapy escalation remains unclear. Routine reporting of outcome measures which incorporate cognitive impairment, fatigue, pain, and mental health will permit more accurate quantification of residual disability and comprehensive comparisons between international multicentre cohorts, and enable future meta-analyses with the aim of developing evidence-based therapeutic guidelines.

Epileptic Seizures and Right-Sided Hippocampal Swelling as Presenting Symptoms of Anti-IgLON5 Disease: A Case Report and Systematic Review of the Literature

Background and Objective

Anti-IgLON5 disease is an uncommon neurological disorder characterized by diverse clinical manifestations. Although many relevant cases have been reported, our understanding of this disorder is still quite restricted. We present a rare case of anti-IgLON5 disease and performed a comprehensive systematic review of all published cases to expand the clinical spectrum of this disorder.

Methods

We report a 61-year-old woman with an atypical presentation of epileptic seizures with abnormal signals in her right hippocampus on brain magnetic resonance imaging (MRI). A systematic review was performed of electronic databases, including PubMed, EMBASE, China National Knowledge Infrastructure (CNKI), WanFang and VIP China Science.

Results

We identified 161 cases from 65 publications. With heterogeneous clinical manifestations, we found that bulbar dysfunction, sleep apnea, gait instability and neurocognitive and behavioral symptoms are the most common symptoms of anti-IgLON5 disease. Anti-IgLON5 antibodies presented a higher positive rate and titer in the serum than in the cerebrospinal fluid (CSF). Haplotype DRB1*10:01-DQB1*05:01 is highly correlated with anti-IgLON5 disease. Only 38 patients have presented distinctive MRI alterations (26.2%). Approximately half of the cases are responsive to immunosuppressive or immunomodulatory treatment.

Conclusion

Anti-IgLON5 disease is characterized by various clinical manifestations and laboratory findings. Immunotherapy may be effective in treating anti-IgLON5 disease, but the results are far from satisfactory. Studies with larger sample sizes are required to improve the current understanding of this disorder.

Rare antibody-mediated and seronegative autoimmune encephalitis: An update

Paralleling advances with respect to more common antibody-mediated encephalitides, such as anti-N-methyl-D-aspartate receptor (NMDAR) and anti-leucine-rich glioma-inactivated 1 (LGI1) Ab-mediated encephalitis, the discovery and characterisation of novel antibody-mediated encephalitides accelerated over the past decade, adding further depth etiologically to the spectrum of antibody-mediated encephalitis. Herein, we review the major mechanistic, clinical features and management considerations with respect to anti-γ-aminobutyric acid B (GABA_B)-, anti-α-amino-3-hydroxy-5-methyl-4-isoxazolepropinoic receptor- (AMPAR), anti-GABA_A-, anti-dipeptidyl-peptidase-like protein-6 (DPPX) Ab-mediated encephalitides, delineate rarer subtypes and summarise findings to date regarding seronegative autoimmune encephalitis.

Autoimmune and Paraneoplastic Chorea: A Review of the Literature

Autoimmune chorea syndromes represent a vast array of paraneoplastic, parainfectious and idiopathic disorders. It is increasingly apparent that familiarity with these disorders is critically important, as they may be treatable or may be part of a syndrome requiring further work-up and monitoring. These disorders are mediated by an aberrant immunologic attack with resultant neuronal dysfunction, manifesting as chorea. These conditions are typically accompanied by other neurologic or systemic manifestations. In this review we outline the clinical features, epidemiologic factors, and delineate the specific antibodies associated with each of these autoimmune mediated disorders. We highlight up to date information regarding this heterogeneous group of disorders, including a discussion of parainfectious Sydenham's chorea; paraneoplastic syndromes associated with CRMP-5 (collapsin response mediated protein-5/CV2) and ANNA-1 (antineuronal nuclear antibody / Hu) antibodies, in addition to neuronal antibody-associated disorders including anti-NMDAR, LGI1 (leucine-rich glioma inactivated-1) and CASPR2 (contactin associated protein-2). We discuss the more recently described entities of IgLON5, which has evidence of both immunologic and degenerative pathophysiology, in addition to PDE-10A antibody-associated chorea. We also outline chorea secondary to systemic diseases including Systemic Lupus Erythematosus (SLE) and Primary Antiphospholipid Syndrome (PAPS). We provide a framework for diagnosis and treatment.

Pilot Study of the Effects of Chronic Intracerebroventricular Infusion of Human Anti-IgLON5 Disease Antibodies in Mice

Background: Anti-IgLON5 disease is a rare late-onset neurological disease associated with autoantibodies against IgLON5, neuronal accumulation of phosphorylated Tau protein (p-Tau), and sleep, respiratory, and motor alterations. Purpose: We performed a pilot study of whether the neuropathological and clinical features of anti-IgLON5 disease may be recapitulated in mice with chronic intracerebroventricular infusion of human anti-IgLON5 disease IgG (Pt-IgG). Methods: Humanized transgenic hTau mice expressing human Tau protein and wild-type (WT) control mice were infused intracerebroventricularly with Pt-IgG or with antibodies from a control subject for 14 days. The sleep, respiratory, and motor phenotype was evaluated at the end of the antibody infusion and at least 30 days thereafter, followed by immunohistochemical assessment of p-Tau deposition. Results: In female hTau and WT mice infused with Pt-IgG, we found reproducible trends of diffuse neuronal cytoplasmic p-Tau deposits in the brainstem and hippocampus, increased ventilatory period during sleep, and decreased inter-lick interval during wakefulness. These findings were not replicated on male hTau mice. Conclusion: The results of our pilot study suggest, but do not prove, that chronic ICV infusion of mice with Pt-IgG may elicit neuropathological, respiratory, and motor alterations. These results should be considered as preliminary until replicated in larger studies taking account of potential sex differences in mice.

Anti-IgLON5 Disease - The Current State of Knowledge and Further Perspectives

Anti-IgLON5 disease is a relatively new neurological entity with the first cases reported in 2014. So far, less than 70 articles on this topic have been published. Due to its unspecific symptomatology, diverse progression, novelty and ambiguous character, it remains a difficulty for both clinical practitioners and scientists. The aim of this review is to summarize the current knowledge concerning anti-IgLON5 disease; mechanisms underlying its cause, symptomatology, clinical progression, differential diagnosis and treatment, which could be helpful in clinical practice and future research.

Increased Intrathecal B and Plasma Cells in Patients With Anti-IgLON5 Disease: A Case Series

Background and Objectives

Despite detection of autoantibodies, anti-IgLON5 disease was historically considered a tau-associated neurodegenerative disease, with limited treatment options and detrimental consequences for the patients. Observations in increasing case numbers hint toward underlying inflammatory mechanisms that, early detection provided, open a valuable window of opportunity for therapeutic intervention. We aimed to further substantiate this view by studying the CSF of patients with anti-IgLON5.

Methods

We identified 11 patients with anti-IgLON5 from our database and compared clinical, MRI, and CSF findings with a cohort of 20 patients with progressive supranuclear palsy (PSP) (as a noninflammatory tauopathy) and 22 patients with functional neurologic disorder.

Results

Patients with anti-IgLON5 show inflammatory changes in routine CSF analysis, an increase in B-lymphocyte frequency, and the presence of plasma cells in comparison to the PSP-control group and functional neurologic disease controls. Patients with intrathecal plasma cells showed a clinical response to rituximab.

Discussion

Our findings indicate the importance of inflammatory mechanisms, in particular in early and acute anti-IgLON5 cases, which may support the use of immune-suppressive treatments in these cases. The main limitation of the study is the small number of cases due to the rarity of the disease.

[Clinical features of anti-IgLON5 disease]

Anti-IgLON5 diseases were first reported in 2014 as sleep disorders such as parasomnia and obstructive sleep apnea. The pathological findings were suggestive of tauopathies and eight clinical subtypes have been reported so far. Serum and cerebrospinal fluid anti-IgLON5 antibodies should be measured in patients with sleep-related disorders with parasomnia as well as in patients with movement disorders, motor neuron disease or dementia with characteristic parasominia. The prognosis is generally poor, but some patients have been reported to improve with immunotherapy. Early diagnosis and early immunotherapy may improve the prognosis.

Expanding the clinical spectrum of anti-IgLON5 disease: A multicenter retrospective study

BACKGROUND

We conducted this study to describe detailed the clinical characteristics, ancillary test results and treatment response of a group of Chinese patients with anti-IgLON5 disease.

METHODS

We recruited 13 patients with positive IgLON5 antibodies in serum and/or cerebrospinal fluid from nine tertiary referral centers. Patients were enrolled from February 2017 to July 2021. We retrospectively collected information on the presenting and main symptoms, treatment response and follow-up outcomes.

RESULTS

The median age of onset for symptoms was 60 (range: 33-73) years and six of the 13 patients were females. The predominant clinical presentations included sleep disturbance (eight patients) and cognitive impairment (seven patients), followed by movement disorders (six patients). Parainfectious cause seemed plausible. Notably, we identified the first case of possible Epstein-Barr virus (EBV)-related anti-IgLON5 disease. Coexisting neural autoantibodies were identified in two patients. Furthermore, two patients had other autoimmune diseases. The IgG subclass was determined in four patients, including two with dominant IgG4 subtype and two with dominant IgG1 subtype. Additionally, 10 patients were treated with immunotherapy and four patients exhibited improvement. Overall, six of 10 patients for whom follow-up results were assessable had favorable clinical outcomes (modified Rankin Scale score ≤2).

CONCLUSIONS

The clinical spectrum of anti-IgLON5 disease is variable. Our results highlight a boarder spectrum of anti-IgLON5 disease.

Short- and Long-Lived Autoantibody-Secreting Cells in Autoimmune Neurological Disorders

As B cells differentiate into antibody-secreting cells (ASCs), short-lived plasmablasts (SLPBs) are produced by a primary extrafollicular response, followed by the generation of memory B cells and long-lived plasma cells (LLPCs) in germinal centers (GCs). Generation of IgG4 antibodies is T helper type 2 (Th2) and IL-4, -13, and -10-driven and can occur parallel to IgE, in response to chronic stimulation by allergens and helminths. Although IgG4 antibodies are non-crosslinking and have limited ability to mobilize complement and cellular cytotoxicity, when self-tolerance is lost, they can disrupt ligand-receptor binding and cause a wide range of autoimmune disorders including neurological autoimmunity. In myasthenia gravis with predominantly IgG4 autoantibodies against muscle-specific kinase (MuSK), it has been observed that one-time CD20⁺ B cell depletion with rituximab commonly leads to long-term remission and a marked reduction in autoantibody titer, pointing to a short-lived nature of autoantibody-secreting cells. This is also observed in other predominantly IgG4 autoantibody-mediated neurological disorders, such as chronic inflammatory demyelinating polyneuropathy and autoimmune encephalitis with autoantibodies against the Ranvier paranode and juxtaparanode, respectively, and extends beyond neurological autoimmunity as well. Although IgG1 autoantibody-mediated neurological disorders can also respond well to rituximab induction therapy in combination with an autoantibody titer drop, remission tends to be less long-lasting and cases where titers are refractory tend to occur more often than in IgG4 autoimmunity. Moreover, presence of GC-like structures in the thymus of myasthenic patients with predominantly IgG1 autoantibodies against the acetylcholine receptor and in ovarian teratomas of autoimmune encephalitis patients with predominantly IgG1 autoantibodies against the N‐methyl‐d‐aspartate receptor (NMDAR) confers increased the ability to generate LLPCs. Here, we review available information on the short-and long-lived nature of ASCs in IgG1 and IgG4 autoantibody-mediated neurological disorders and highlight common mechanisms as well as differences, all of which can inform therapeutic strategies and personalized medical approaches.

Autoimmune encephalitis: clinical spectrum and management

Autoimmune encephalitis defines brain inflammation caused by a misdirected immune response against self-antigens expressed in the central nervous system. It comprises a heterogeneous group of disorders that are at least as common as infectious causes of encephalitis. The rapid and ongoing expansion of this field has been driven by the identification of several pathogenic autoantibodies that cause polysymptomatic neurological and neuropsychiatric diseases. These conditions often show highly distinctive cognitive, seizure and movement disorder phenotypes, making them clinically recognisable. Their early identification and treatment improve patient outcomes, and may aid rapid diagnosis of an underlying associated tumour. Here we summarise the well-known autoantibody-mediated encephalitis syndromes with neuronal cell-surface antigens. We focus on practical aspects of their diagnosis and treatment, offer our clinical experiences of managing such cases and highlight more basic neuroimmunological advances that will inform their future diagnosis and treatments.

Functional Recovery in Autoimmune Encephalitis: A Prospective Observational Study

Background

Prospective observations of functional recovery are lacking in patients with autoimmune encephalitis defined by antibodies against synaptic proteins and neuronal cell surface receptors.

Methods

Adult patients with a diagnosis of autoimmune encephalitis were included into a prospective registry. At 3, 6 and 12 months of follow-up, the patients’ modified Rankin Scale (mRS) was obtained.

Results

Patients were stratified into three groups according to their antibody (Ab) status: anti-NMDAR-Ab (n=12; group I), anti-LGI1/CASPR2-Ab (n=35; group II), and other antibodies (n=24; group III). A comparably higher proportion of patients in group I received plasma exchange/immunoadsorption and second line immunosuppressive treatments at baseline. A higher proportion of patients in group II presented with seizures. Group III mainly included patients with anti-GABA_BR-, anti-GAD65- and anti-GlyR-Ab. At baseline, one third of them had cancer. Patients in groups I and III had much higher median mRS scores at 3 months compared to patients in group II. A median mRS of 1 was found at all follow-up time points in group II.

Conclusions

The different dynamics in the recovery of patients with certain autoimmune encephalitides have important implications for clinical trials. The high proportion of patients with significant disability at 3 months after diagnosis in groups I and III points to the need for improving treatment options. More distinct scores rather than the mRS are necessary to differentiate potential neurological improvements in patients with anti-LGI1-/CASPR2-encephalitis.

Neurodegeneration Induced by Anti-IgLON5 Antibodies Studied in Induced Pluripotent Stem Cell-Derived Human Neurons

Anti-IgLON5 disease is a progressive neurological disorder associated with autoantibodies against a neuronal cell adhesion molecule, IgLON5. In human postmortem brain tissue, the neurodegeneration and accumulation of hyperphosphorylated tau (p-tau) are found. Whether IgLON5 antibodies induce neurodegeneration or neurodegeneration provokes an immune response causing inflammation and antibody formation remains to be elucidated. We investigated the effects of anti-IgLON5 antibodies on human neurons. Human neural stem cells were differentiated for 14–48 days and exposed from Days 9 to 14 (short-term) or Days 13 to 48 (long-term) to either (i) IgG from a patient with confirmed anti-IgLON5 antibodies or (ii) IgG from healthy controls. The electrical activity of neurons was quantified using multielectrode array assays. Cultures were immunostained for β-tubulin III and p-tau and counterstained with 4′,6-Diamidine-2′-phenylindole dihydrochloride (DAPI). To study the impact on synapses, cultures were also immunostained for the synaptic proteins postsynaptic density protein 95 (PSD95) and synaptophysin. A lactate dehydrogenase release assay and nuclei morphology analysis were used to assess cell viability. Cultures exposed to anti-IgLON5 antibodies showed reduced neuronal spike rate and synaptic protein content, and the proportion of neurons with degenerative appearance including p-tau (T205)-positive neurons was higher when compared to cultures exposed to control IgG. In addition, cell death was increased in cultures exposed to anti-IgLON5 IgG for 21 days. In conclusion, pathological anti-IgLON5 antibodies induce neurodegenerative changes and cell death in human neurons. This supports the hypothesis that autoantibodies may induce the neurodegenerative changes found in patients with anti-IgLON5-mediated disease. Furthermore, this study highlights the potential use of stem cell-based in vitro models for investigations of antibody-mediated diseases. As anti-IgLON5 disease is heterogeneous, more studies with different IgLON5 antibody samples tested on human neurons are needed.

Management of autoimmune encephalitis

PURPOSE OF REVIEW

Autoimmune encephalitides are established diagnoses in contemporary neurology. Their management poses a regular challenge for almost all neurologists. One may ask if the concept of 1st line and 2nd line treatment is still up to date, which new data on the antibody-defined encephalitis types exist, and how to organize long-term management.

RECENT FINDINGS

The 1st line/2nd line concept of initial immunological intervention is accepted worldwide. A randomized controlled trial confirmed that one 1st line compound (intravenous immunoglobulins) is superior to a placebo in patients with antibodies against leucine-rich glioma inactivated protein 1. Rituximab, a 2nd line compound, is increasingly and apparently successfully used in treating different types of autoimmune encephalitis. It may find its place even earlier in the treatment cascade. Long-term management needs to be improved and is under development.

SUMMARY

There have been no groundbreaking new developments in the field. The published experience confirms existing suggestions. Aspects of long-term management including rehabilitation measures and counseling about driving eligibility require further research.

Musical hallucinations: a rare and atypical presentation of anti-IgLON5 disease responsive to immunosuppressive therapy

IgLON5 antibodies are typically associated with the insidious onset of sleep disorder, parasomnia, gait disturbance and abnormal movements, with variable response to immunosuppressive therapy. We describe a case of a 50-year-old man who presented with acute speech difficulties, headache and focal seizures followed by well-formed visual hallucinations, and later, musical hallucinations of mainstream popular music. MRI of the brain demonstrated right temporal lobe changes with corresponding epileptiform activity seen on electroencephalogram. Subsequently, IgLON5 antibodies were detected in the serum. The patient was treated with anticonvulsants, as well as azathioprine with a tapering oral prednisone course with a complete resolution of the symptoms. Our case demonstrates an unusual presentation of the rare but increasingly described anti-IgLON5 disease, with musical hallucinations. The case highlights the variable and evolving clinical phenotypes that can be seen in autoimmune central nervous system disorders.

Sleep Disturbances Associated with Neurological Autoimmunity

Associations between sleep disorders and neurological autoimmunity have been notably expanding recently. Potential immune-mediated etiopathogenesis has been proposed for various sleep disorders including narcolepsy, Kleine-Levin syndrome, and Morvan syndrome. Sleep manifestations are also common in various autoimmune neurological syndromes, but may be underestimated as overriding presenting (and potentially dangerous) neurological symptoms often require more urgent attention. Even so, sleep dysfunction has been described with various neural-specific antibody biomarkers, including IgLON5; leucine-rich, glioma-inactivated protein 1 (LGI1); contactin-associated protein 2 (CASPR2); N-methyl-D-aspartate (NMDA)-receptor; Ma2; dipeptidyl-peptidase-like protein-6 (DPPX); alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPA-R); anti-neuronal nuclear antibody type-1 (ANNA-1, i.e., Hu); anti-neuronal nuclear antibody type-2 (ANNA-2, i.e., Ri); gamma-aminobutyric acid (GABA)-B-receptor (GABA-B-R); metabotropic glutamate receptor 5 (mGluR5); and aquaporin-4 (AQP-4). Given potentially distinctive findings, it is possible that sleep testing could potentially provide objective biomarkers (polysomnography, quantitative muscle activity during REM sleep, cerebrospinal fluid hypocretin-1) to support an autoimmune diagnosis, monitor therapeutic response, or disease progression/relapse. However, more comprehensive characterization of sleep manifestations is needed to better understand the underlying sleep disruption with neurological autoimmunity.

Sleep disorders in autoimmune encephalitis

Sleep disorders in people with autoimmune encephalitis have received little attention, probably overshadowed by the presence of other neurological and psychiatric symptoms in this group of conditions. However, sleep disorders are frequent, often severe, and usually persist beyond the acute disease stage, interfering with patients' recovery and quality of life. Because autoimmune encephalitis can affect any brain network involved in sleep initiation and regulation, all types of sleep disorders can occur, with varying distinct associations, frequency, and intensity. Anti-IgLON5 and anti-NMDA receptor encephalitis exemplify two diseases in which sleep disorders are prominent. In anti-IgLON5 disease, sleep disorders were the core symptoms that led to the description of this disease, whereas in anti-NMDA receptor encephalitis, sleep disorders vary according to the disease stage along with other neuropsychiatric symptoms. Comprehensive, systematic, multicentre studies are needed to characterise sleep disorders and their mechanisms in autoimmune encephalitis.