COVID-19 and Multiple Sclerosis: Predisposition and Precautions in Treatment: SN Comprehensive Clinical Medicine, by Shaghayegh Sadeghmousavi and Nima Rezaei.
https://doi.org/10.1007/s42399-020-00504-9

Study Conclusion:
“Multiple Sclerosis is a chronic inflammatory disease of the CNS with an autoimmune etiology. The pathology of this disease starts with increased migration of autoreactive lym- phocytes across the BBB. Regulatory defects allow these cells to transit from physiological states to a pathological cascade. Both genetic and environmental factors in MS patients can cause this impairment of the regulatory lymphocytes functions to suppress effector cells. Microbial infections can act as triggers for inducing autoimmunity and clinical disease manifestations in genetically predisposed individuals. Studies have suggested a robust relationship between viral infections and exacerbations of MS. Based on the aforementioned studies, COVID-19 carries additional reasons for concern because of taking immunosuppressive therapies in MS patients and also the fact that viral infections may contribute to MS exacerbation and relapses as an environmental factor.  This study provides some insights regarding the impact of COVID-19 disease on actively treated patients with MS.
For clarification of the exact relationship between COVID- 19 and MS, further studies are needed. Meanwhile, clinicians should take care of patients with MS during the pandemic regarding the possible reciprocal association between the MS and COVID-19.”

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7467844/