Polyautoimmunity in a Greek cohort of multiple sclerosis

Objectives The aim of this study was to assess the existence of polyautoimmunity in a Greek cohort of multiple sclerosis ( MS ), particularly multiple autoimmune syndrome (MAS), i.e., the presence of three or more distinct autoimmune disorders ( AD s) in the same individual. Methods Cross‐sectional control study. Results The overall prevalence of polyautoimmunity in 2140 MS patients (female to male ratio: 2.1:1) was 8.3% (vs 6.07% in 1580 matched control participants, P  = 0.008) mainly due to differences in autoimmune thyroid disorders ( AITD ) and vitiligo. The prevalence of MAS was 1.0%. The most frequent diseases encountered in MS were organ‐specific AD s. There was no statistical difference in the total rates of AD s between female and male MS patients. There were higher rates of AITD in women ( P  = 0.004) and higher rates of iritis ( P  = 0.039) and ankylosing spondylitis ( P  = 0.003) in men. MS was diagnosed in the same year with AD in 7.4% of patients with additional AD s, earlier than AD in 42.0% and later than AD in 50.6%. Conclusion Polyautoimmunity and particularly MAS occur more frequently in MS patients than in control participants indicating that MS may be part of a generalized susceptibility to autoimmunity. Therefore, polyautoimmunity may be implicated in the etiopathogenesis of MS ‐related AD s, with a potential impact on relative therapeutic strategies.