At the end of 2019, the COVID-19 pandemic began, which at the time of writing continues to be a serious problem for many areas of medicine, including neurology. Since patients with multiple sclerosis (MS) often exhibit motor disability and receive disease-modifying therapy (DMT), which has an immunosuppressive effect, it is plausible that this will affect the susceptibility of MS patients to COVID-19, as well as the course of this disease. However, current data indicate that the use of DMT does not cause negative prognosis in COVID-19 sufferers, but the motor disability progression associated with MS does. In this study, we present the case reports of 4 patients with relapsing-remitting MS, who developed COVID-19, and despite the use of DMT the course of the disease was mild. Two patients were treated with dimethyl fumarate, one with Interferon β1b and one with glatiramer acetate. One of the patients using dimethyl fumarate had lymphopenia. All patients had symptoms of COVID-19 from the nervous system, the most frequent being headache, which occurred in all patients. The aim of this article is to present a case series of four patients with MS and COVID-19, and to discuss the available literature on COVID-19 in patients with MS, with particular consideration of the impact of DMT. Copyright © 2020 Elsevier B.V. All rights reserved.