The relative frequency of Myasthenia Gravis in patients with Multiple Sclerosis and Neuromyelitis Optica

Abstract Background: Co-occurrence of autoimmune diseases have always been an area of interest due to common underlying immunopathologic mechanisms. In this study, we assess the relative frequency of myasthenia gravis (MG) in patients with multiple sclerosis (MS) and neuromyelitis optica (NMO). Methods: Records of patients with MS and NMO who visited the Isfahan MS center were screened. The data of patients with comorbid MG was used to calculate relative frequency. Results: The relative frequency of MG in our sample MS and NMO population was 0.34% and 5%, respectively, which is higher than the reported prevalence of MG alone in the general population (0.0005-0.024%). Conclusion: The higher frequency of MG in MS and NMO populations compared to the general frequency of the disease may be due to common immunopathologic mechanisms that underly the diseases. Regulatory T cells, the complement pathway, matrix metalloproteinases, and B cells play critical roles in each disease and share common features in MS and MG. The complement system also plays a central role in NMO and MG. The relative frequency of MG in patients with MS and NMO is higher than of that reported in the general population (0.34% and 5%, respectively).