Effect of systemic therapies on serum inflammatory biomarkers in hidradenitis suppurativa

Aim: An objective, reliable biomarker is needed to effectively monitor the heterogeneous course of hidradenitis suppurativa (HS). This study investigated the potential of serum cathelicidin, LL-37, S100A7 and S100A15 as biomarkers by (i) comparing their levels in HS patients versus healthy controls, (ii) examining changes after treatment, and (iii) evaluating their correlation with clinical disease severity. Methods: Using a case-control design with a 3-month prospective follow-up, serum biomarker levels were measured using ELISA. Disease severity was assessed by Hurley stage, IHS4, while treatment response was determined using HiSCR criteria. Results: A total of 56 participants (40 HS and 16 controls) were included. Serum levels of all biomarkers were significantly lower in HS patients compared to healthy controls (p<0.001). However, only cathelicidin levels showed a significant positive correlation with Hurley stage (p=0.042, r=0.32) and IHS4 (p=0.016, r=0.38). Following a 3-month treatment, serum cathelicidin levels significantly decreased (p<0.001), particularly in the group receiving biological therapy. Conclusion: Our findings suggest that serum cathelicidin is a dynamic biomarker that correlates with disease severity in HS and is significantly modulated in response to treatment, especially with biologics. While serum levels of others were significantly different between HS and controls, they did not perform as consistently as cathelicidin in tracking disease activity or treatment response. We conclude that cathelicidin is a promising candidate for monitoring disease activity and assessing treatment response in HS, and further large-scale, prospective, multicenter studies are needed to confirm this potential. Keywords: hidradenitis suppurativa, cathelicidin, antimicrobial peptides, biomarker, IHS4, biologic therapy