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Objectives: Pathogenic variants in presenilin 1 (PSEN1) are related to early-onset Alzheimer disease (AD) and may occur as de novo variants. In comparison with sporadic forms, it can present with psychiatric manifestations, seizures, myoclonus, and focal presentation. Because PSEN1 can occur in young patients who lack a family history of neurologic disorders and because these symptoms are also frequent in autoimmune encephalitis (AE), diagnosis may be overlooked. Our aim was to demonstrate the challenge in diagnosing young patients with neurodegenerative diseases that simulate AE., Methods: We describe a case of a young patient with insidious progressive dementia, myoclonus, seizures, and aphasia, with no family history of dementia, along with signs suggestive of neuroinflammation on brain MRI and CSF examination., Results: She was initially misdiagnosed as having AE. Further investigation was performed, leading to the discovery of a novel and de novo pathogenic variant in PSEN1., Discussion: This case demonstrates the importance of considering PSEN1 in young patients with insidious progressive dementia with atypical clinical and neuroimaging features, even in patients without a family history of neurologic disorders. Not adhering to published criteria of possible and probable AE and overinterpretation of subtle inflammatory findings in CSF and MRI contribute to misdiagnosis.

Background:  Autoimmune encephalitis (AIE) is a group of inflammatory diseases characterized by the presence of antibodies against neuronal and glial antigens, leading to subacute psychiatric symptoms, memory complaints, and movement disorders. The patients are predominantly young, and delays in treatment are associated with worse prognosis., Objective:  With the support of the Brazilian Academy of Neurology (Academia Brasileira de Neurologia, ABN) and the Brazilian Society of Child Neurology (Sociedade Brasileira de Neurologia Infantil, SBNI), a consensus on the diagnosis and treatment of AIE in Brazil was developed using the Delphi method., Methods:  A total of 25 panelists, including adult and child neurologists, participated in the study., Results:  The panelists agreed that patients fulfilling criteria for possible AIE should be screened for antineuronal antibodies in the serum and cerebrospinal fluid (CSF) using the tissue-based assay (TBA) and cell-based assay (CBA) techniques. Children should also be screened for anti-myelin oligodendrocyte glucoprotein antibodies (anti-MOG). Treatment should be started within the first 4 weeks of symptoms. The first-line option is methylprednisolone plus intravenous immunoglobulin (IVIG) or plasmapheresis, the second-line includes rituximab and/or cyclophosphamide, while third-line treatment options are bortezomib and tocilizumab. Most seizures in AIE are symptomatic, and antiseizure medications may be weaned after the acute stage. In anti-N-methyl-D-aspartate receptor (anti-NMDAR) encephalitis, the panelists have agreed that oral immunosuppressant agents should not be used. Patients should be evaluated at the acute and postacute stages using functional and cognitive scales, such as the Mini-Mental State Examination (MMSE), the Montreal Cognitive Assessment (MoCA), the Modified Rankin Scale (mRS), and the Clinical Assessment Scale in Autoimmune Encephalitis (CASE)., Conclusion:  The present study provides tangible evidence for the effective management of AIE patients within the Brazilian healthcare system., Competing Interests: LAD reports that she has received a grant for the Brazilian Autoimmune Encephalitis Network (Rede Brasileira de Encefalites Autoimunes), from Laboratório Fleury., (The Author(s). This is an open access article published by Thieme under the terms of the Creative Commons Attribution 4.0 International License, permitting copying and reproduction so long as the original work is given appropriate credit (https://creativecommons.org/licenses/by/4.0/).)

Autoimmune encephalitis (AE) comprises a group of diseases mediated by antibodies against neuronal cell surface or synaptic antigens, such as ion channels or neurotransmitter receptors. New clinical syndromes and their associated antibodies were and are still being characterized over the last two decades. The fact that their main clinical features are interdisciplinary, - encompassing neuropsychiatric symptoms, cognitive dysfunction, epileptic seizures, movement and sleep disorders - has led to a surge of interest in this field. Some of these diseases present with a well-defined syndrome, being recognizable on clinical grounds. Correct diagnosis is important since AE are potentially treatable diseases, despite their severity. On the other hand, an increasing number of neuronal antibodies being described casts doubt upon the way we should utilize antibody testing and interpret results. In this article we review, summarize and update the current knowledge on antibody mediated encephalitis.

The main objective of this article is to improve our understanding of the differences and similarities of these two anti-gamma-aminobutyric acid receptor encephalitis, anti-GABAaR and anti-GABAbR. The data were systematically collected and we found 26 studies: seven studies and 37 patients corresponded to anti-GABAaR encephalitis, and 21 manuscripts and 116 patients were diagnosed with anti-GABAbR encephalitis. Both anti-GABAR encephalitis were marked by prominent seizures. Anti-GABAaR patients were younger and showed multifocal encephalitis. On the other hand, anti-GABAbR patients were older and showed temporal limbic encephalitis. Tumor occurred in a fifth of anti-GABAaR encephalitis and in half of anti-GABAbR encephalitis. The main tumor associated with anti-GABAbR encephalitis is SCLC, whereas the most common tumor associated with anti-GABAaR encephalitis was thymoma. Our data confirms the differences in clinical features between both encephalitis., (Copyright © 2021. Published by Elsevier B.V.)

Anti-NMDA receptor encephalitis (NMDARE), an autoimmune encephalitis associated with autoantibodies against the N-methyl-D-aspartate (NMDA) receptor, affects predominantly young women and is associated with psychiatric symptoms, seizures, movement disorders, and autonomic instability. Traditional treatments of anti-NMDA receptor encephalitis involve corticosteroids, intravenous immunoglobulin, plasmapheresis, cyclophosphamide, and rituximab. However, many controversies remain in the treatment for NMDA receptor encephalitis, such as optimal timing and combination of different immunotherapies, the role of newer strategies (e.g., bortezomib or tocilizumab) for severe and refractory patients, and the need or not for long-term immunosuppression. Our goal was to perform a scoping review to discuss the controversial topics of immunotherapy for NMDA receptor encephalitis and propose operational definitions to guide clinical practice and future research in the field. [ABSTRACT FROM AUTHOR]