Comorbid autoimmune disorders in people with multiple sclerosis: A retrospective cohort study.

Most autoimmune disorders, including multiple sclerosis (MS), are influenced by shared genetic and environmental factors. We conducted a cohort study of people with MS to calculate the frequency of comorbid autoimmune disorders and characterize this cohort. Autoimmune diseases were present in 30 (8.6%) of 349 patients. The most prevalent diagnoses were autoimmune thyroiditis, type 1 diabetes mellitus, psoriasis, and inflammatory bowel disease. We found no association with demographic or clinical factors. In our cohort, autoimmune disorders were not uncommon. Identifying such comorbidities in people with MS can be determinant for understanding disease mechanisms, treatment decisions and disease management.