280 https://oamjms.eu/index.php/mjms/index Scientifc Foundation SPIROSKI, Skopje, Republic of Macedonia Open Access Macedonian Journal of Medical Sciences. 2022 Sep 24; 10(C):280-284. https://doi.org/10.3889/oamjms.2022.10632 eISSN: 1857-9655 Category: C - Case Reports Section: Case Report in Internal Medicine Anti-NMDAR Encephalitis and Myasthenia Gravis Post-COVID-19 Vaccination: Cases of Possible COVID-19 Vaccination-Associated Autoimmunity Astra Dea Simanungkalit 1 * , Vivien Puspitasari 1 , Jacqueline Tasha Margono 2 , Pamela Tiffani 2 , Reza Stevano 2 1 Department of Neurology, Siloam Hospitals Lippo Village, Tangerang, Indonesia; 2 Department of Neurology, Faculty of Medicine, Universitas Pelita Harapan, Tangerang, Indonesia Abstract BACKGROUND: Coronavirus disease 2019 (COVID-19) continues to be a global issue. While immunizations comprise an important line of defense, adverse effects may occur. We report two cases of autoimmune conditions affecting the nervous system, anti-N-Methyl-D-Aspartate-receptor (NMDAR) encephalitis and myasthenia gravis (MG), that developed in close association with COVID-19 vaccination. CASE REPORT: In our frst case, a 29-year-old woman presents with recurrent seizures, auditory hallucinations, psychiatric symptoms, and autonomic abnormalities, with an onset of 1 day after receiving the second dose of inactivated SARS-CoV-2 whole virus vaccine. CSF analysis and electroencephalogram (EEG) were consistent with anti-NMDAR encephalitis. In our second case, a 23-year-old woman presents with ocular ptosis, diplopia, hoarseness, and fatigability, which frst appeared 1-day after her frst dose of inactivated SARS-CoV-2 whole virus vaccine. Electromyography (EMG) results established a defnite diagnosis of MG. CONCLUSION: To the best of our knowledge, this is the frst report of anti-NMDAR encephalitis and MG associated with inactivated SARS-CoV-2 whole virus vaccine. In both cases, COVID-19 vaccination appears to be the only remarkable feature of history. The authors postulate that COVID-19 vaccination may trigger underlying defects or induce failure of positive and negative selection, which may lead to autoreactivity and subsequent autoimmunity. However, further studies are required to confrm this possibility. Edited by: Mirko Spiroski Citation: Dea Simanungkalit A, Puspitasari V, Margono JT, Tiffani P, Stevano R. Anti-NMDAR Encephalitis and Myasthenia Gravis Post COVID-19 Vaccination: Cases of Possible COVID-19 Vaccination-Associated Autoimmunity. Open-Access Maced J Med Sci. 2022 Sep 24; 10(C):280- 284. https://doi.org/10.3889/oamjms.2022.10632 Keywords: Anti-NMDAR encephalitis; Myasthenia gravis; COVID-19; Vaccination; Case report *Correspondence: Astra Dea Simanungkalit, Department of Neurology, Siloam Hospitals Lippo Village, Tangerang, Indonesia. E-mail: simanungkalit.astra@gmail.com Received: 06-Jul-2022 Revised: 03-Aug-2022 Accepted: 14-Sep-2022 Copyright: © 2022 Astra Dea Simanungkalit, Vivien Puspitasari, Jacqueline Tasha Margono, Pamela Tiffani, Reza Stevano Funding: This research did not receive any fnancial support Competing Interest: The authors have declared that no competing interest exists Open Access: This is an open-access article distributed under the terms of the Creative Commons Attribution- NonCommercial 4.0 International License (CC BY-NC 4.0) Introduction Two years have lapsed since the World Health Organization (WHO) has declared coronavirus disease 2019 (COVID-19) a global pandemic on March of 2020. At the time of writing, there have been more than 5.2 million deaths, and 262 million infections reported worldwide [1]. Immunizations comprise an important line of defense against the global pandemic, with hopes of suppressing transmission as well as disease-related morbidity and mortality. A variety of vaccines against COVID-19, each with different mechanisms of inducing immunity, are widely available in circulation, and millions of individuals across the globe have received immunizations and its benefts [1], [2]. However as with all drugs, adverse effects are bound to occur. Several side effects have been reported following COVID-19 vaccination ranging from mild (e.g., fatigue and myalgia) to severe (e.g., myocarditis and thromboembolic events). Rarely, there have also been reports of COVID-19 vaccine-induced autoimmunity [3]. We report the case of two autoimmune conditions affecting the nervous system, anti-N-Methyl-D-Aspartate-receptor (NMDAR) encephalitis and myasthenia gravis, that developed in close association following COVID-19 vaccination. To the best of our knowledge, this is the frst report of anti- NMDAR encephalitis and myasthenia gravis thought to be associated with the inactivated SARS-CoV-2 whole virus vaccine. Anti-NMDAR encephalitis is a rare form of autoimmune or paraneoplastic encephalitis commonly found in late adolescence, with a strong female preponderance (80% of cases). The appearance of anti-NMDAR encephalitis is closely associated with previous viral infections (such as herpes simplex virus, Japanese encephalitis virus, and recently SARS-CoV-2) [4], [5], [6], [7] or tumors (namely, ovarian teratoma, which is present in 45% of female cases) [8], although 37%–50% of cases are of unknown etiology [4], [8], [9]. The clinical manifestations of anti-NMDAR encephalitis can typically be divided into two stages. The early stage consists of psychiatric symptoms, cognitive impairment, and/or seizures, while the advanced stage is characterized by altered consciousness, movement disorders, and autonomic dysfunction. Within the 1st month, nearly 90% of patients will experience symptoms such as behavioral or cognitive Since 2002