Anti-GAD Encephalitis Following COVID-19 Vaccination: A Case Report

Since December 2020, a significantly higher number of people worldwide have been vaccinated for coronavirus disease 2019 (COVID-19). Neurological complications have been reported after these vaccines, although a definitive causal relationship has not been proven in the available literature. We describe a 51-year-old man presenting with anti-glutamic acid decarboxylase (anti-GAD) antibody positive autoimmune encephalitis with progressive cognitive impairment and behavioral abnormalities, presenting shortly after the second dose of mRNA COVID-19 vaccine, possibly representing a serious vaccine related adverse event. Response to high-dose steroid and intravenous immunoglobulin treatment was positive. As many people around the world have been vaccinated against COVID-19, this case shows that autoimmune encephalitis and even anti-GAD antibody positive autoimmune encephalitis can develop as a side effect after this new vaccine, but with early diagnosis and appropriate treatment, the clinic can have a good prognosis. Observational studies with large numbers of patients are needed to explain causality.