Causal relationship between metabolic syndrome and hidradenitis suppurativa: A two-sample bidirectional Mendelian...

Observational studies have suggested an association between metabolic syndrome (MetS) and hidradenitis suppurativa (HS), but whether this relationship is causal remains unclear. Elucidating the causal direction could provide insights into disease mechanisms and potential interventions. We performed bidirectional two-sample Mendelian randomization (MR) using summary statistics from genome-wide association studies (GWAS) of MetS and HS. For validation, we replicated the MetS analysis using data from an independent GWAS. We applied multiple MR methods, primarily inverse variance-weighted (IVW) regression, and conducted sensitivity analyses to assess heterogeneity and pleiotropy. The MR analysis demonstrated MetS causally increased HS risk (IVW odds ratio [OR], 1.428 [95% CI, 1.193-1.710]; p < 0.001), with consistent evidence from sensitivity analyses. However, HS did not appear to causally influence MetS risk (IVW OR, 1.008 [95% CI, 0.988-1.028]; p = 0.438). This study provides evidence that MetS causally increases the risk of developing HS. However, we found no evidence for a causal relationship in the reverse direction from HS to MetS. Further research is warranted to elucidate the mechanisms underlying the identified causal association between MetS and subsequent HS development.