The association between epilepsy and myasthenia gravis has rarely been reported, and when it has been reported, it has only been in a small case series. The aim of the present study was to report the frequency of epilepsy and myasthenia gravis and to describe a case series of patients with myasthenia gravis and epilepsy, focusing on their clinical characteristics and searching for a possible physiopathological mechanism. A retrospective, observational, adult center study was conducted in 2022. Patients were recruited from the database of the outpatient clinic of the Myasthenia Gravis and Epilepsy Unit of the Neurology Service, Hospital Universitari de Bellvitge. Five patients were included. The frequency of epilepsy in the myasthenia gravis cohort was 5/469 (1.1%), and the frequency of myasthenia gravis in the epilepsy cohort was 5/1432 (0.35%). All patients suffered from focal epilepsy, mainly temporo-central, which was drug-resistant in 3/5 Myasthenia gravis, which was generalized and with exacerbations in 3/5. Three patients were thymectomized (anatomopathology: thymic hyperplasia). Other autoimmune diseases were found in two (40%). Epilepsy onset preceded myasthenia gravis onset in all patients. Both diseases were considered autoimmune-related in 3/5, related to genetic predisposition due to altered innate immune system in 1/5, and due to chance or to treatment in 1/5. Epilepsy and myasthenia gravis are only infrequently associated. In adult patients, epilepsy onset precedes myasthenia onset in most cases. In some cases, epilepsy has an autoimmune etiology and coexists with other autoimmune conditions.

Introduction: The association between epilepsy and myasthenia gravis has rarely been reported, and only in small case series. Objective: To report the frequency of epilepsy and myasthenia gravis and to describe a case series of patients with myasthenia gravis and epilepsy, focusing on their clinical characteristics and searching for a possible physiopathological mechanism. Methods: A retrospective, observational, adult center study was conducted in 2022. Patients were recruited from the database of the outpatient clinic of the Myasthenia Gravis unit and Epilepsy unit. Results: Five patients were included. Frequency of epilepsy in the myasthenia gravis cohort was 5/469 (1.1%), and of myasthenia gravis in the epilepsy cohort was 5/1432 (0.35%). All patients suffered focal epilepsy, mainly fronto-central, and drug-resistant in half of them. Myasthenia gravis was generalized and with exacerbations in half of them. Three patients were thymectomized. Other autoimmune diseases were found in 2 (40%). Epilepsy onset preceded myasthenia gravis onset in all patients. Both diseases were considered autoimmune-related in 3/5 (60%). Conclusion: Epilepsy and myasthenia gravis are only infrequently associated. In adult patients, epilepsy onset precedes myasthenia onset in most cases. In some cases, epilepsy has an autoimmune aetiology and coexists with other autoimmune conditions.