Association of autoimmune comorbidities in persons with multiple sclerosis from a population-based study with genetic linkage

Background: Comorbidities are a critical concern for clinicians in both the treatment and diagnosis of multiple sclerosis. Autoimmune diseases, including multiple sclerosis, often co-occur within individuals. However, most studies examining the incidence or prevalence of autoimmune diseases in persons with multiple sclerosis compared to healthy controls have used relatively small sample sets, with only a few being population-based. Objectives: To analyze the co-occurrence of other autoimmune diseases in persons with multiple sclerosis and determine whether common genetic susceptibility factors contribute to the co-occurrence of autoimmune diseases. Methods: We conducted a population-based study using administrative health records to include all residents of Piedmont, an Italian Region with about 4.3 million inhabitants, identifying individuals with multiple sclerosis and 14 other autoimmune diseases. For a subset of persons with multiple sclerosis with available genome-wide genotyping data, we investigated the influence of their genetic backgrounds using a polygenic risk score. Results: The prevalence of all 14 tested autoimmune diseases was higher in persons with multiple sclerosis compared to those without multiple sclerosis. Furthermore, persons with multiple sclerosis with autoimmune disease comorbidities had a higher polygenic risk score compared to persons with multiple sclerosis without comorbidities. Conclusion: Our findings confirm the co-occurrence of multiple sclerosis with several autoimmune diseases, and suggest that shared genetic susceptibility factors may influence this association.