Multiple sclerosis is a chronic inflammatory disease of the central nervous system, caused by an autoimmune reaction. Treatment options have largely increased over the years. In this article, we present two clinical cases. Patient A has a classic relapsing remitting course of multiple sclerosis with satisfactory effect on second line therapy. Patient B had a stable disease course until a new relapse occurred after the initiation of TNF-alpha blocking therapy because of Crohn's disease. The co-occurrence of multiple auto-immune diseases creates challenges, but also opportunities in choosing the right treatment strategy.