Supplementary Material for: The Effects of Immune Checkpoint Inhibitors on Hidradenitis Suppurativa: A Scoping Review

Background
Hidradenitis suppurativa (HS) is a debilitating skin disease marked by recurrent abscesses and chronic inflammation. Immune checkpoint inhibitors (ICIs) are widely used oncologic treatments that can provoke immune-mediated effects. ICI potential to precipitate HS onset or influence HS disease activity remains uncharacterized. We aim to characterize the timing, clinical features, severity, and outcomes of HS in this context.
Methods
Scoping review according to PRISMA guidelines was conducted. Studies were identified through PubMed and MEDLINE searches and were eligible if they reported at least 1 case of HS onset or worsening in the setting of ICI therapy.
Results
Five publications comprising 13 patients were included. Pembrolizumab was the most frequently used ICI (46.2%). Eight individuals (61.5%) had pre-existing HS, of whom 3 (37.5%) experienced flares during therapy. Five patients (38.5%) developed new-onset HS after ICI initiation, within 2-4 months. Treatment approaches varied and included topicals and systemic therapies for HS. Four patients (30.8%) experienced complete resolution of HS lesions following ICI discontinuation.
Conclusions
ICI therapy may precipitate new-onset HS or exacerbate pre-existing disease in a subset of patients. Increased clinical vigilance and early dermatologic involvement may support timely diagnosis, optimize management, and preserve continuity of oncologic care.