Cutaneous Reactions to Checkpoint Inhibitors in Oncodermatology

Conclusions

• Cutaneous immune-related adverse events from checkpoint inhibitors are common and will likely become more frequent as these drugs are used more broadly.
• Skin toxicities often affect barrier tissues and include a wide range of morphologies that can overlap, appear together, or evolve over time.
• There are no reliable rules based on timing alone, because dermatologic irAEs can occur early, late, or even after checkpoint inhibitor therapy has stopped.
• Patients with pre-existing inflammatory skin disease are at higher risk for flares or new cutaneous irAEs, and these eruptions may be more severe and faster to appear.
• Because checkpoint inhibitor eruptions can mimic one another and shift phenotype, ongoing follow-up and a flexible diagnostic approach are essential.
• Lesional skin in these reactions shows broad immune activation, with evidence for Th1, Th2, Th17, tissue-resident memory T-cell, and monocyte/macrophage involvement depending on the subtype.
• Despite their heterogeneity, these eruptions may share common inflammatory pathways such as cytokine elevation and monocyte/macrophage signatures.
• Developing a skin irAE is associated with better cancer outcomes and improved survival, making cutaneous toxicity a potentially favorable prognostic marker.
• Systemic corticosteroids may be associated with worse oncologic outcomes, so steroid-sparing approaches are often preferred when feasible.
• Overall, managing checkpoint inhibitor skin toxicity requires close monitoring, careful phenotype recognition, and treatment strategies that control inflammation without compromising antitumor benefit.