Association of Multiple Sclerosis with Psoriasis: A Systematic Review and Meta-Analysis of Observational Studies

Background: Previous studies have reported the occurrence of psoriasis together with multiple sclerosis (MS). Although similar predisposing genes and pathomechanisms have been hypothesized, the relationship between the two remains obscure. Objective: The aim of this systematic review and meta-analysis was to investigate the association between psoriasis and MS. Methods: We searched MEDLINE, Embase, and CENTRAL in July 2018 for case–control, cross-sectional, or cohort studies that examined either the odds or risk of psoriasis in subjects with multiple sclerosis. The risk of bias of included studies was assessed using the Newcastle–Ottawa Scale. A random-effects model meta-analysis was used to calculate the odds ratio (OR) for case–control/cross-sectional studies and hazard ratio (HR) for cohort studies. Results: We included 10 publications that reported a total of 11 studies (5 case–control, 4 cross-sectional and 2 cohort studies). The case–control and cross-sectional studies included 18,456 MS patients and 870,149 controls, while the two cohort studies involved 25,187 MS patients and 227,225 controls in total. Three studies were rated with a high risk of bias in comparability, non-response rate, and selection of controls. MS was associated with increased odds (OR 1.29; 95% confidence interval [CI] 1.14–1.45) and risk for psoriasis (HR 1.92; 95% CI 1.32–2.80). Conclusion: Patients with MS display both increased prevalence and incidence of psoriasis.