It has become increasingly clear in recent years that the gut flora, genetic factors and environmental factors play an important role in disease and health. Whether the interplay between the intestinal flora, genetic factors and environmental factors has an influence on the onset and course of MS has not yet been sufficiently researched. That is why research into this is being conducted at the Radboudumc in Nijmegen. This research is called the GEMSIM study: Genetics in Multiple Sclerosis in Interaction with the gut Microbiome.