Multiple Sclerosis (MS) is a chronic disease of the central nervous system (CNS) characterized by inflammation, demyelination and axonal loss. This disease typically strikes young adults, especially women. There are four types of MS according to their relapsing or progressive pattern that include relapsing-remitting (RRMS), secondary progressive (SPMS), primary progressive (PPMS), and progressive relapsing (PRMS). In most patients, the disease has a relapsing-remitting course during the first years. Within 10 years, approximately 50% of patients progress to SPMS. The aetiology of MS is not well understood, but it is likely multifactorial, combining both genetic and environmental factors. Recently, the literature on the risk factors for MS has grown substantially. They indicate that a combination of a genetic predisposition, exposure to Epstein-Barr virus, cigarette smoking, and reduced sunlight exposure/vitamin D levels is involved. Authorized first-line treatments are considered equally effective, and include interferon beta and glatiramer acetate. They are primarily directed against inflammation, and might fail to adequately control disease activity in some patients. In that case, it has been recommended to switch these patients early to a therapy of higher efficacy. Currently, 13 different drugs with ten different active components are licensed in the European Union (EU) and the United States (US) for the treatment of MS.