Nivolumab-induced hidradenitis suppurativa: a case report.

We present a 44-year-old man with metastatic clear cell renal cell cancer undergoing treatment with nivolumab immunotherapy. Three months post-initiation, he developed symmetric recurrent nodules and boils in intertriginous areas, diagnosed as stage II hidradenitis suppurativa of the groin and gluteal cleft. The progressive course, lesion symmetry and location, worsening with nivolumab infusions, and biopsy findings supported the diagnosis. Hidradenitis suppurativa pathogenesis involves immune dysregulation marked by elevated IL17 and neutrophil-dominated inflammation [1]. Immune checkpoint inhibitors, including anti-PD1 agents like nivolumab, are linked to immune-related adverse events related to widespread T cell activation, potentially increasing IL17 signaling associated with HS [2,3]. Clinicians should be aware of, and observant for anti-PD1-induced HS, a rare immune-related adverse event, in patients undergoing immune checkpoint inhibitor therapy.