cGAS activation in classical dendritic cells causes autoimmunity in TREX1-deficient mice.

Detection of cytosolic DNA by the cyclic GMP-AMP (cGAMP) synthase (cGAS)-stimulator of interferon genes (STING) pathway provides immune defense against pathogens and cancer but can also cause autoimmunity when overactivated. The exonuclease three prime repair exonuclease 1 (TREX1) degrades DNA in the cytosol and prevents cGAS activation by self-DNA. Loss-of-function mutations of the TREX1 gene are linked to autoimmune diseases such as Aicardi-Goutières syndrome, and mice deficient in TREX1 develop lethal inflammation in a cGAS-dependent manner. In order to determine the type of cells in which cGAS activation drives autoinflammation, we generated conditional cGAS knockout mice on the Trex1-/- background. Here, we show that genetic ablation of the cGAS gene in classical dendritic cells (cDCs), but not in macrophages, was sufficient to rescue Trex1-/- mice from all observed disease phenotypes including lethality, T cell activation, tissue inflammation, and production of antinuclear antibodies and interferon-stimulated genes. These results show that cGAS activation in cDC causes autoinflammation in response to self-DNA accumulated in the absence of TREX1.

Different Patterns of Autoantibody Secretion by Peripheral Blood Mononuclear Cells in Autoimmune Nodopathies.

BACKGROUND AND OBJECTIVES: Autoimmune nodopathies with antibodies against the paranodal proteins show a distinct phenotype of a severe sensorimotor neuropathy. In some patients, complete remission can be achieved after treatment with rituximab whereas others show a chronic course. For optimal planning of treatment, predicting the course of disease and therapeutic response is crucial. METHODS: We stimulated peripheral blood mononuclear cells in vitro to find out whether secretion of specific autoantibodies may be a predictor of the course of disease and response to rituximab. RESULTS: Three patterns could be identified: In most patients with anti-Neurofascin-155-, anti-Contactin-1-, and anti-Caspr1-IgG4 autoantibodies, in vitro production of autoantibodies was detected, indicating autoantigen-specific memory B cells and short-lived plasma cells/plasmablasts as the major source of autoantibodies. These patients generally showed a good response to rituximab. In a subgroup of patients with anti-Neurofascin-155-IgG4 autoantibodies and insufficient response to rituximab, no in vitro autoantibody production was found despite high serum titers, indicating autoantibody secretion by long-lived plasma cells outside the peripheral blood. In the patients with anti-pan-Neurofascin autoantibodies-all with a monophasic course of disease-no in vitro autoantibody production could be measured, suggesting a lack of autoantigen-specific memory B cells. In some of them, autoantibody production by unstimulated cells was detectable, presumably corresponding to high amounts of autoantigen-specific plasmablasts-well in line with a severe but monophasic course of disease. DISCUSSION: Our data suggest that different B-cell responses may occur in autoimmune nodopathies and may serve as markers of courses of disease and response to rituximab.

Epitope landscape in autoimmune neurological disease and beyond.

Autoantibody binding has a central role in autoimmune diseases and has also been linked to cancer, infections, and behavioral disorders. Autoimmune neurological diseases remain misclassified also due to an incomplete understanding of the underlying disease-specific epitopes. Such epitopes are crucial for both pathology and diagnosis, but have historically been overlooked. Recent technological advancements have enabled the exploration of these epitopes, potentially opening novel clinical avenues. The precise identification of novel B and T cell epitopes and their autoreactivity has led to the discovery of autoantigen-specific biomarkers for patients at high risk of autoimmune neurological diseases. In this review, we propose utilizing newly available synthetic and cellular-surface display technologies and guide epitope-focused studies to unlock the potential of disease-specific epitopes for improving diagnosis and treatments. Additionally, we offer recommendations to guide emerging epitope-focused studies to broaden the current landscape.

[Autoimmune glial fibrillary acidic protein astrocytopathy]. / Astrocitopatía autoinmune asociada a proteína ácida fibrilar glial.

Autoimmune glial fibrillary acidic protein (GFAP) astrocytopathy was described for the first time in 2016. The most common clinical manifestation is meningoencephalomyelitis associated with a characteristic imaging pattern that allows diagnostic suspicion and its confirmation through determination of antibodies in serum and cerebrospinal fluid (CSF). We present a case of a 35-year-old patient with involvement of the central and peripheral nervous system and a recent diagnosis of thyroid cancer, which compared to the compatible clinical picture of meningoencephalomyelitis, characteristic findings on MRI and after the exclusion of alternative pathologies, we finally arrived at the diagnosis by the positive determination of anti-GFAP in CSF. The patient underwent surgical treatment and radioactive iodine for the diagnosed thyroid tumor and she subsequently received treatment with corticosteroids with partial improvement of the neurological symptomatology. We emphasize that in this pathology the MRI images usually depict a characteristic pattern, although not pathognomonic, it is necessary to consider other causes. Before a high suspicion of this entity due to the clinical and imaging picture, it is convenient to measure the antibody in CSF, given the greater sensitivity and specificity compared to its serum screening, in order to arrive to the definitive etiological diagnosis as it was done in the clinical case that is presented.

La astrocitopatía autoinmune asociada a proteína ácida fibrilar glial (GFAP) fue descripta por primera vez en el año 2016. La manifestación clínica más frecuente es la meningoencefalomielitis asociado a un patrón imagenológico característico que permite la sospecha diagnóstica y su confirmación mediante la determinación de los anticuerpos en suero y en líquido cefalorraquídeo (LCR). Presentamos el caso de una paciente de 35 años con compromiso del sistema nervioso a nivel central y periférico y un reciente diagnóstico de cáncer de tiroides, que frente al cuadro clínico compatible de meningoencefalomielitis, los hallazgos característicos en resonancia magnética y luego de la exclusión de enfermedades alternativas, finalmente se arribó al diagnóstico por la determinación positiva de anti GFAP en LCR. Realizó tratamiento quirúrgico y con iodo radioactivo por su tumor hallado y posteriormente recibió tratamiento con corticoides con mejoría parcial de la signo-sintomatología neurológica. Destacamos que en esta enfermedad las imágenes por resonancia magnética presentan un patrón característico, aunque no patognomónico, siendo necesario considerar otras causas. Ante una alta sospecha de esta entidad por el cuadro clínico e imagenológico, es conveniente realizar dosaje del anticuerpo en LCR, dada la mayor sensibilidad y especificidad en comparación con su pesquisa en suero, con el fin de arribar al diagnóstico etiológico definitivo como en el caso clínico presentado.

Lymphocytes in autoimmune encephalitis: Pathogenesis and therapeutic target.

Autoimmune encephalitis (AE) is an inflammatory disease of the central nervous system characterized by the production of various autoimmune antibodies targeting neuronal proteins. The pathogenesis of AE remains elusive. Accumulating evidence suggests that lymphocytes, particularly B and T lymphocytes, play an integral role in the development of AE. In the last two decades, autoimmune neural antibodies have taken center stage in diagnosing AE. Recently, increasing evidence has highlighted the importance of T lymphocytes in the onset of AE. CD4+ T cells are thought to influence disease progression by secreting associated cytokines, whereas CD8+ T cells exert a cytotoxic role, causing irreversible damage to neurons mainly in patients with paraneoplastic AE. Conventionally, the first-line treatments for AE include intravenous steroids, intravenous immunoglobulin, and plasma exchange to remove pathogenic autoantibodies. However, a minority of patients are insensitive to conventional first-line treatment protocols and suffer from disease relapse, a condition referred to as refractory AE. In recent years, new treatments, such as rituximab or CAAR-T, which target pathogenic lymphocytes in patients with AE, have offered new therapeutic options for refractory AE. This review aims to describe the current knowledge about the function of B and T lymphocytes in the pathophysiology of AE and to summarize and update the immunotherapy options for treating this disease.

Autologous hematopoietic stem cell transplantation for pediatric autoimmune neurologic disorders.

Autologous hematopoietic stem cell transplantation (aHSCT) may be effective in carefully selected pediatric patients with multiple sclerosis (MS), neuromyelitis optica (NMO), and chronic inflammatory demyelinating polyneuropathy (CIDP). aHSCT for pediatric MS (same as for adults) is performed to eradicate inflammatory autoreactive cells with lympho-ablative regimens and restore immune tolerance. Its therapeutic effect in MS relies on various mechanisms: (1) the immunosuppressive conditioning regimen prior to aHSCT was able to eradicate the autoreactive cells and (2) the regeneration/renewal of the immune system to reset the aberrant immune response against self-antigens. The aHSCT procedure includes the following different steps, as described in this chapter: patient selection through careful pretransplant screening, "wash-out" period from previous treatments, mobilization of hematopoietic stem cells (HSC), conditioning regimen, HSC infusion, and posttransplant monitoring for early and late complications. Moreover, specific aspects of pediatric population undergoing aHSCT are described. According to the available evidence, aHSCT appears to be safe in pediatric MS, obtaining disease control for a prolonged time after the procedure. A reasonable approach in this setting includes the application of less toxic treatments while reserving aHSCT procedure for patients with severe/refractory forms of the disease. The EBMT considers MS, NMO, and CIDP in pediatric patients within the category of the clinical option (CO), where candidates for aHSCT can be selected on the basis of careful consideration of individual case history in the multidisciplinary setting.

Economics of hematopoietic stem cell transplant in immune-mediated neurologic autoimmune diseases.

Autologous hematopoietic stem cell transplantation (AHSCT) is a therapeutic procedure for autoimmune diseases which suppresses inflammation and resets the immune system, thereby halting disease activity and disability progression in treatment-resistant patients. This chapter reviews existing guidelines and health economic evaluations of AHSCT for multiple sclerosis (MS) and presents a cost-utility analysis from the UK NHS and personal social services perspective comparing AHSCT with disease-modifying therapies (DMTs) in patients with highly active relapsing-remitting MS (RRMS) based on the only published randomized controlled trial, "MIST," in this population. Over a 5-year time horizon, AHSCT was dominant (more effective and less costly) over the DMTs in MIST. At a threshold of £20,000 per QALY, there was a 100% probability that AHSCT was cost-effective. This result is explained by the high ongoing costs of DMTs compared with the up-front cost of AHSCT, combined with the high effectiveness of AHSCT. When compared with natalizumab, the result did not change; AHSCT remained dominant. These results support current guideline recommendations regarding AHSCT for highly active RRMS. The cost-effectiveness of AHSCT in progressive and aggressive MS and other immune-mediated neurologic diseases remains uncertain due to a lack of health economic analyses, reflecting the limited clinical evidence base.

Overview and Diagnostic Approach in Autoimmune Neurology.

OBJECTIVE: The field of autoimmune neurology is rapidly evolving. This article reviews the epidemiology and pathophysiology as well as current approaches to clinical and paraclinical assessment, testing paradigms, and general principles of treatment. LATEST DEVELOPMENTS: Improved recognition of autoimmune diagnoses among patients who have phenotypically diverse, subacute onset neurologic presentations is facilitated by disease-specific antibody biomarker discovery. These antibodies have varying associations with paraneoplastic causation (from no association to greater than 70% positive predictive value), immunotherapy responses, and outcomes. To simplify assessment in an increasingly complex discipline, neurologic phenotype-specific serum and CSF antibody evaluations are recommended. Clinical trials have led to the approval of monoclonal therapies for neuromyelitis optica spectrum disorder (NMOSD) and are underway for N-methyl-d-aspartate (NMDA) receptor and leucine-rich glioma inactivated protein 1 (LGI1) encephalitides. ESSENTIAL POINTS: Autoimmune neurology is now a mainstream subspecialty, consisting of disorders with diverse presentations detectable using antibody testing of serum and CSF. Early and sustained immunotherapy (eg, corticosteroids, intravenous immunoglobulin [IVIg], plasma exchange) is recommended and may be supplemented by immune suppressants (eg, rituximab or cyclophosphamide) to sustain responses and optimize outcomes.

Autoimmune Encephalitis.

OBJECTIVE: This article focuses on the clinical features and diagnostic evaluations that accurately identify patients with ever-expanding forms of antibody-defined encephalitis. Forms of autoimmune encephalitis are more prevalent than infectious encephalitis and represent treatable neurologic syndromes for which early immunotherapies lead to the best outcomes. LATEST DEVELOPMENTS: A clinically driven approach to identifying many autoimmune encephalitis syndromes is feasible, given the typically distinctive features associated with each antibody. Patient demographics alongside the presence and nature of seizures, cognitive impairment, psychiatric disturbances, movement disorders, and peripheral features provide a valuable set of clinical tools to guide the detection and interpretation of highly specific antibodies. In turn, these clinical features in combination with serologic findings and selective paraclinical testing, direct the rationale for the administration of immunotherapies. Observational studies provide the mainstay of evidence guiding first- and second-line immunotherapy administration in autoimmune encephalitis and, whereas these typically result in some clinical improvements, almost all patients have residual neuropsychiatric deficits, and many experience clinical relapses. An improved pathophysiologic understanding and ongoing clinical trials can help to address these unmet medical needs. ESSENTIAL POINTS: Antibodies against central nervous system proteins characterize various autoimmune encephalitis syndromes. The most common targets include leucine-rich glioma inactivated protein 1 (LGI1), N-methyl-d-aspartate (NMDA) receptors, contactin-associated proteinlike 2 (CASPR2), and glutamic acid decarboxylase 65 (GAD65). Each antibody-associated autoimmune encephalitis typically presents with a recognizable blend of clinical and investigation features, which help differentiate each from alternative diagnoses. The rapid expansion of recognized antibodies and some clinical overlaps support panel-based antibody testing. The clinical-serologic picture guides the immunotherapy regime and offers valuable prognostic information. Patient care should be delivered in conjunction with autoimmune encephalitis experts.

Autoimmune Neuromuscular Disorders Associated With Neural Antibodies.

OBJECTIVE: This article reviews autoimmune neuromuscular disorders and includes an overview of the diagnostic approach, especially the role of antibody testing in a variety of neuropathies and some other neuromuscular disorders. LATEST DEVELOPMENTS: In the past few decades, multiple antibody biomarkers associated with immune-mediated neuromuscular disorders have been reported. These biomarkers are not only useful for better understanding of disease pathogenesis and allowing more timely diagnosis but may also aid in the selection of an optimal treatment strategy. ESSENTIAL POINTS: Recognition of autoimmune neuromuscular conditions encountered in inpatient or outpatient neurologic practice is very important because many of these disorders are reversible with prompt diagnosis and early treatment. Antibodies are often helpful in making this diagnosis. However, the clinical phenotype and electrodiagnostic testing should be taken into account when ordering antibody tests or panels and interpreting the subsequent results. Similar to other laboratory investigations, understanding the potential utility and limitations of antibody testing in each clinical setting is critical for practicing neurologists.

Pediatric Autoimmune Neurologic Disorders.

OBJECTIVE: This article discusses common principles in diagnosing and managing autoimmune neurologic conditions in children. LATEST DEVELOPMENTS: The key to improving outcomes in all patients with autoimmune neurologic diseases is making an early diagnosis, promptly initiating treatment, and identifying patients who will benefit from long-term maintenance treatment. Some neuroinflammatory syndromes can be diagnosed with an antibody biomarker (eg, aquaporin-4 antibodies, N-methyl-d-aspartate [NMDA] receptor antibodies), whereas others require clinical diagnostic criteria (eg, multiple sclerosis, opsoclonus-myoclonus syndrome). A proportion of children will be labeled as seronegative, and further investigations for other inflammatory or monogenetic etiologies need to be carried out in parallel with treating the central nervous system inflammation. Time to treatment and treatment escalation were shown to correlate with outcomes in many patients with these disorders. The choice and duration of treatment should be evaluated considering side effects and risks in the short and long terms. The presence of a highly inflammatory disease process in children supports the use of highly effective disease-modifying therapies in pediatrics. ESSENTIAL POINTS: The phenotypes of pediatric autoimmune neurologic conditions may change across different age groups, as the brain is still actively developing. In general, the presentation in children is more inflammatory, but overall disability is lower, likely because of better neuroplasticity and repair. Convincing evidence has increasingly emerged to support the biological rationale that effective immunosuppressive therapies used in adult neuroimmunology are equally effective in children.

Autoimmune Movement Disorders.

OBJECTIVE: This article reviews the clinical and antibody spectrum of autoimmune cerebellar ataxia and other autoimmune movement disorders. It highlights characteristic phenotypes and red flags to the diagnosis and how these rare, but treatable, disorders are integrated into a differential diagnosis. LATEST DEVELOPMENTS: An increasing number of neuronal antibodies have been identified in patients with cerebellar ataxia, for example, against Kelch-like protein 11 (KLHL11), seizure-related 6 homolog-like 2, septin-3 and septin-5, or tripartite motif containing protein 9 (TRIM9), TRIM46, and TRIM67. Ig-like cell adhesion molecule 5 (IgLON5) antibody-associated syndromes have emerged as an important alternative diagnostic consideration to various neurodegenerative diseases such as Huntington disease or atypical parkinsonism. Opsoclonus-myoclonus syndrome emerged as the most relevant parainfectious movement disorder related to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). ESSENTIAL POINTS: Autoimmune cerebellar ataxia and other autoimmune movement disorders encompass a broad spectrum of different clinical syndromes, antibodies, and immunopathophysiologic mechanisms. Clinical acumen is key to identifying the cases that should undergo testing for neuronal antibodies. Given the overlap between phenotypes and antibodies, panel testing in serum and CSF is recommended.

Therapeutic Approach to Autoimmune Neurologic Disorders.

OBJECTIVE: Autoimmune neurologic disorders encompass a broad category of diseases characterized by immune system attack of the central, peripheral, or autonomic nervous systems. This article provides information on both acute and maintenance immunotherapy used to treat autoimmune neurologic disorders as well as a review of symptomatic management and special considerations when caring for patients with these diseases. LATEST DEVELOPMENTS: Over the past 20 years, more than 50 antibodies have been identified and associated with autoimmune neurologic disorders. Although advances in diagnostic testing have allowed for more rapid diagnosis, the therapeutic approach to these disorders has largely continued to rely on expert opinion, case series, and case reports. With US Food and Drug Administration (FDA) approval of biologic agents to treat neuromyelitis optica spectrum disorder (NMOSD) and myasthenia gravis as well as ongoing clinical trials for the treatment of autoimmune encephalitis, the landscape of immunotherapy options continues to expand. Consideration of the unique pathogenesis of individual autoimmune neurologic disorders as well as the mechanism of action of the diverse range of treatment options can help guide treatment decisions today while evidence from clinical trials informs new therapeutics in the future. ESSENTIAL POINTS: Recognizing patients who have a clinical history and examination findings concerning for autoimmune neurologic disorders and conducting a thorough and directed imaging and laboratory evaluation aimed at ruling out mimics, identifying specific autoimmune syndromes, and screening for factors that may have an impact on immunotherapy choices early in the clinical course are essential to providing optimal care for these patients. Providers must consider immunotherapy, symptomatic treatment, and a multidisciplinary approach that addresses each patient's unique needs when treating patients with autoimmune neurologic disorders.

Human stem cell-derived neurons and astrocytes to detect novel auto-reactive IgG response in immune-mediated neurological diseases.

Background and objectives: Up to 46% of patients with presumed autoimmune limbic encephalitis are seronegative for all currently known central nervous system (CNS) antigens. We developed a cell-based assay (CBA) to screen for novel neural antibodies in serum and cerebrospinal fluid (CSF) using neurons and astrocytes derived from human-induced pluripotent stem cells (hiPSCs). Methods: Human iPSC-derived astrocytes or neurons were incubated with serum/CSF from 99 patients [42 with inflammatory neurological diseases (IND) and 57 with non-IND (NIND)]. The IND group included 11 patients with previously established neural antibodies, six with seronegative neuromyelitis optica spectrum disorder (NMOSD), 12 with suspected autoimmune encephalitis/paraneoplastic syndrome (AIE/PNS), and 13 with other IND (OIND). IgG binding to fixed CNS cells was detected using fluorescently-labeled antibodies and analyzed through automated fluorescence measures. IgG neuronal/astrocyte reactivity was further analyzed by flow cytometry. Peripheral blood mononuclear cells (PBMCs) were used as CNS-irrelevant control target cells. Reactivity profile was defined as positive using a Robust regression and Outlier removal test with a false discovery rate at 10% following each individual readout. Results: Using our CBA, we detected antibodies recognizing hiPSC-derived neural cells in 19/99 subjects. Antibodies bound specifically to astrocytes in nine cases, to neurons in eight cases, and to both cell types in two cases, as confirmed by microscopy single-cell analyses. Highlighting the significance of our comprehensive 96-well CBA assay, neural-specific antibody binding was more frequent in IND (15 of 42) than in NIND patients (4 of 57) (Fisher's exact test, p = 0.0005). Two of four AQP4+ NMO and four of seven definite AIE/PNS with intracellular-reactive antibodies [1 GFAP astrocytopathy, 2 Hu+, 1 Ri+ AIE/PNS)], as identified in diagnostic laboratories, were also positive with our CBA. Most interestingly, we showed antibody-reactivity in two of six seronegative NMOSD, six of 12 probable AIE/PNS, and one of 13 OIND. Flow cytometry using hiPSC-derived CNS cells or PBMC-detected antibody binding in 13 versus zero patients, respectively, establishing the specificity of the detected antibodies for neural tissue. Conclusion: Our unique hiPSC-based CBA allows for the testing of novel neuron-/astrocyte-reactive antibodies in patients with suspected immune-mediated neurological syndromes, and negative testing in established routine laboratories, opening new perspectives in establishing a diagnosis of such complex diseases.

Antibodies in Autoimmune Neuropathies: What to Test, How to Test, Why to Test.

Autoimmune neuropathies are a heterogeneous group of immune-mediated disorders of the peripheral nerves. Guillain-Barré syndrome (GBS) and chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) are the archetypal acute and chronic forms. Over the past few decades, pathogenic antibodies targeting antigens of the peripheral nervous system and driving peripheral nerve damage in selected patients have been described. Moreover, the detection of these antibodies has diagnostic and therapeutic implications that have prompted a modification of the GBS and CIDP diagnostic algorithms. GBS diagnosis is based in clinical criteria, and systematic testing of anti-ganglioside antibodies is not required. Nonetheless, a positive anti-ganglioside antibody test may support the clinical suspicion when diagnosis of GBS (GM1 IgG), Miller Fisher (GQ1b IgG), or acute sensory-ataxic (GD1b IgG) syndromes is uncertain. Anti-myelin-associated glycoprotein (MAG) IgM and anti-disialosyl IgM antibodies are key in the diagnosis of anti-MAG neuropathy and chronic ataxic neuropathy, ophthalmoplegia, M-protein, cold agglutinins, and disialosyl antibodies spectrum neuropathies, respectively, and help differentiating these conditions from CIDP. Recently, the field has been boosted by the discovery of pathogenic antibodies targeting proteins of the node of Ranvier contactin-1, contactin-associated protein 1, and nodal and paranodal isoforms of neurofascin (NF140, NF186, or NF155). These antibodies define subgroups of patients with specific clinical (most importantly poor or partial response to conventional therapies and excellent response to anti-CD20 therapy) and pathologic (node of Ranvier disruption in the absence of inflammation) features that led to the definition of the "autoimmune nodopathy" diagnostic category and to the incorporation of nodal/paranodal antibodies to clinical routine testing. The purpose of this review was to provide a practical vision for the general neurologist of the use of antibodies in the clinical assessment of autoimmune neuropathies.

Pediatric Autoimmune Encephalitis: A Nationwide Study in Latvia.

BACKGROUND: Autoimmune encephalitis (AE) is the third most common encephalitis in children. Diagnosis can be challenging due to overlapping and diverse clinical presentations as well as various investigation results. This study aims to characterize the clinical, diagnostic features, as well as treatment and outcomes of AE in children and determine the incidence of pediatric AE in Latvia. METHODS: The study was conducted at the Children's Clinical University Hospital in Riga. The study participants were patients under the age of 18 years diagnosed with AE from 2014 to 2022. Data regarding clinical characteristics, investigation findings, treatment strategy, and outcomes were retrospectively collected from the medical history data system. RESULTS: We included 18 pediatric patients diagnosed with AE. The mean incidence of pediatric AE in Latvia was 0.56 per 100,000 children. Most patients (66.6%) had seronegative AE. In the seropositive group, the most common was anti-methyl-D-aspartate receptor AE, with two patients having other antibodies. The most prevalent clinical features were personality change, cognitive impairment, autonomic dysfunction, and movement disorders. The majority of patients (58.8%) received first-line treatment only. More than half (55.6%) of our AE patient group had long-term sequelae. CONCLUSIONS: Our study shows that the pediatric AE incidence in Latvia is similar to what has been previously reported in other studies. A relatively high proportion of seronegative AE was present in our cohort, indicating that awareness of possible misdiagnosis should be raised. Further research is needed to better understand the underlying mechanisms, characterize clinical features, and determine the treatment of choice in different situations to improve long-term outcomes.

Distinct plasma metabolomic signatures differentiate autoimmune encephalitis from drug-resistant epilepsy.

OBJECTIVE: Differentiating forms of autoimmune encephalitis (AE) from other causes of seizures helps expedite immunotherapies in AE patients and informs studies regarding their contrasting pathophysiology. We aimed to investigate whether and how Nuclear Magnetic Resonance (NMR)-based metabolomics could differentiate AE from drug-resistant epilepsy (DRE), and stratify AE subtypes. METHODS: This study recruited 238 patients: 162 with DRE and 76 AE, including 27 with contactin-associated protein-like 2 (CASPR2), 29 with leucine-rich glioma inactivated 1 (LGI1) and 20 with N-methyl-d-aspartate receptor (NMDAR) antibodies. Plasma samples across the groups were analyzed using NMR spectroscopy and compared with multivariate statistical techniques, such as orthogonal partial least squares discriminant analysis (OPLS-DA). RESULTS: The OPLS-DA model successfully distinguished AE from DRE patients with a high predictive accuracy of 87.0 ± 3.1% (87.9 ± 3.4% sensitivity and 86.3 ± 3.6% specificity). Further, pairwise OPLS-DA models were able to stratify the three AE subtypes. Plasma metabolomic signatures of AE included decreased high-density lipoprotein (HDL, -(CH2)n-, -CH3), phosphatidylcholine and albumin (lysyl moiety). AE subtype-specific metabolomic signatures were also observed, with increased lactate in CASPR2, increased lactate, glucose, and decreased unsaturated fatty acids (UFA, -CH2CH=) in LGI1, and increased glycoprotein A (GlycA) in NMDAR-antibody patients. INTERPRETATION: This study presents the first non-antibody-based biomarker for differentiating DRE, AE and AE subtypes. These metabolomics signatures underscore the potential relevance of lipid metabolism and glucose regulation in these neurological disorders, offering a promising adjunct to facilitate the diagnosis and therapeutics.

Autoimmune glial fibrillary acidic protein astrocytopathy with anti-NMDAR and sulfatide-IgG-positive encephalitis overlap syndrome: A case report and literature review.

RATIONALE: Autoimmune glial fibrillary acidic protein (GFAP) astrocytopathy is a rare autoimmune disease of the central nervous system that affects the meninges, brain, spinal cord, and optic nerves. GFAP astrocytopathy can coexist with a variety of antibodies, which is known as overlap syndrome. Anti-NMDAR-positive encephalitis overlap syndrome has been reported; however, encephalitis overlap syndrome with both anti-NMDAR and sulfatide-IgG positivity has not been reported. PATIENT CONCERNS: The patient was a 50-year-old male who was drowsy and had chills and weak limbs for 6 months. His symptoms worsened after admission to our hospital with persistent high fever, dysphoria, gibberish, and disturbance of consciousness. Positive cerebrospinal fluid NMDA, GFAP antibodies, and serum sulfatide antibody IgG were positive. DIAGNOSES: Autoimmune GFAP astrocytopathy with anti-NMDAR and sulfatide-IgG-positive encephalitis overlap syndrome. INTERVENTIONS: In addition to ventilator support and symptomatic supportive treatment, step-down therapy with methylprednisolone (1000 mg/d, halved every 3 days) and pulse therapy with human immunoglobulin (0.4 g/(kg d) for 5 days) were used. OUTCOMES: After 6 days of treatment, the patient condition did not improve, and the family signed up to give up the treatment and left the hospital. CONCLUSIONS: Patients with autoimmune GFAP astrocytopathy may be positive for anti-NMDAR and sulfatide-IgG, and immunotherapy may be effective in patients with severe conditions. LESSONS: Autoimmune GFAP astrocytopathy with nonspecific symptoms is rarely reported and is easy to be missed and misdiagnosed. GFAP astrocytopathy should be considered in patients with fever, headache, disturbance of consciousness, convulsions, and central infections that do not respond to antibacterial and viral agents. Autoimmune encephalopathy-related antibody testing should be performed as soon as possible, early diagnosis should be confirmed, and immunomodulatory therapy should be administered promptly.

Gluten Ataxia and mGluR1 Autoimmune Encephalitis Presenting as Acute Cerebellar Ataxia: A Case Report.

A Caucasian male in his 60s presented with acute onset of dizziness, dysarthria, and gait ataxia. Upon extensive workup, positive findings were cerebrospinal fluid (CSF) showing lymphocytic pleocytosis with oligoclonal bands, positive celiac disease autoantibodies in blood, a duodenal biopsy indicating lymphocytic infiltration, and positive anti-mGluR1 antibody titers in CSF. The patient was started on a strict gluten-free diet and intravenous immunoglobulin therapy for 5 days and showed mild consecutive improvements each day of treatment. He was discharged after 22 days, and was encouraged to continue gluten adherence, physical and speech therapy, and follow up with neuroimmunology. This report demonstrates that autoimmune encephalitis due to anti-mGluR1antibodies and gluten ataxia are both immune-mediated disorders that should be considered in acute cerebellar ataxia cases. By broadening the differential diagnosis and a comprehensive CSF analysis, identification of gluten ataxia and autoimmune encephalitis were beneficial in the management of this particular patient.