Patients with multiple sclerosis (MS) often present with other immune-mediated disorders, such as ulcerative colitis and type 1 diabetes. Researchers in Sweden analysed data from a large register of patients with MS and their parents to determine whether the risk of such comorbidity has a genetic component. They found that, in contrast to index cases, parents of patients with MS did not show an increased likelihood of having an immune-mediated disorder compared with control parents, arguing against a genetic influence.