To systematically review the literature and conduct a meta-analysis assessing the risk of psoriasis among patients with Multiple Sclerosis(pwMS).

Observational studies have described a possible association between the development of multiple sclerosis (MS) and psoriasis. We performed a systematic review and meta-analysis to investigate the risk of concurrent diagnoses of psoriasis in patients with MS (pwMS).

We systematically searched four databases for case-control, cross-sectional, or cohort studies published up to September 2023, focusing on the relationship between MS and psoriasis. The risk of bias of included studies was assessed using the Newcastle-Ottawa Scale. A random-effects model meta-analysis was used to calculate odds ratios (OR) for case-control/cross-sectional studies, whereas hazard ratios (HR) were calculated for cohort studies, and 95% confidence intervals (95% CIs) were pooled in the meta-analysis. 

Fifteen studies met the inclusion criteria, consisting of three cohort studies, nine case-control studies, and three cross-sectional studies. The analysis encompassed a total of 42,895 pwMS and 21,177,402 controls. The studies were all of high quality, ranging from 7 to 9, and the average result was 7.93. Our findings indicated that pwMS were associated with an increased risk of psoriasis in case-control (OR=1.48; 95% CI: 1.04-2.12, p<0.05) and cross-sectional studies (OR=1.81; 95% CI: 1.03-3.2, p<0.05), as well as a higher risk of psoriasis in cohort studies (HR=1.8; 95% CI: 1.27-2.54, p<0.05).

This meta-analysis found evidence that pwMS have a higher risk of developing psoriasis compared to the general population. Further research is needed to clarify the mechanisms linking these two autoimmune diseases.