TOPLINE:

A study that evaluated the impact of BMI, psoriasis, smoking, inflammatory bowel disease (IBD), and systemic sclerosis (SSc) on the risk for hidradenitis suppurativa (HS) supported a causal effect for increased BMI and IBD. 

METHODOLOGY:

• A two-sample Mendelian randomization (MR) study in 2024-2025, using data from large genetic White European cohorts from genome-wide association studies, explored the effect of BMI, smoking, psoriasis, IBD, and SSc on HS risk, to determine if these risk factors are a cause of HS or are associated with the disease.
• A total of 4814 patients with HS and 1,216,105 control individuals from Denmark, Iceland, Finland, the UK, and the US were studied.
• The analysis included an inverse variance weighted method and an MR-Egger approach to assess the presence of pleiotropic effects between the exposure phenotypes and HS.
• Genetic correlation analyses were performed among 3,592,596 patients to investigate common genetic influences between exposure phenotypes and HS and to identify potential causal relationships.

TAKEAWAY:

• BMI and smoking had genetic correlations with HS (P < .001 for both).
• MR analyses supported a causal effect of increased BMI on HS (odds ratio [OR], 1.20; P < .001) without signs of pleiotropy, but results were inconclusive for smoking (P = .35).
• Among inflammatory conditions, psoriasis and IBD had genetic correlations with HS (P < .001 for both), but SSc did not (P = .22).
• Only IBD showed a causal effect on HS (OR, 1.20; P < .001) without signs of pleiotropy.

IN PRACTICE:

“The findings of this two-sample MR study on the causal relationship among five phenotypes: BMI, smoking, psoriasis, IBD, and SSc (exposures), and HS (outcome), support a causal effect of both BMI and IBD on HS,” the authors wrote. “Because none of the sensitivity analyses revealed signs of pleiotropic effects, the MR should be viewed as inconclusive rather than proof of no causal effect,” they added.

SOURCE:

The study was led by Rune Kjærsgaard Andersen, MD, PhD, Herlev and Gentofte Hospital, Copenhagen University Hospitals, Gentofte, Denmark, and was published online on December 17 in JAMA Dermatology.

LIMITATIONS:

The continuous scale assessment of BMI did not account for potential threshold effects that might drastically increase the risk for HS. The sample was racially homogeneous, limiting the generalizability of the findings. There was potential sample overlap between cohorts. Country-specific residual confounding potentially affected the results. 

DISCLOSURES:

The study was funded by grants from the Leo Foundation and Novo Nordisk Foundation. Andersen reported receiving grants from the Leo Foundation and from the Novo Nordisk Foundation, which also provided grants to one other author. Three authors declared receiving personal speaker fees, advisory fees, and/or grants from LEO Pharma. One author reported having ownership in Novo Nordisk A/S. One author reported as the editor-in-chief of Dermatology. Additional disclosures are noted in the original article.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.