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.