Durable remission of sinonasal mucosal melanoma despite early ICI discontinuation and risankizumab treatment for irAEs.

Sinonasal mucosal melanoma (SNMM) is a rare and aggressive malignancy with few effective treatments. Unlike cutaneous melanoma, responses to immune checkpoint inhibitors (ICIs) in mucosal subtypes are typically modest. We describe a case of metastatic SNMM with a remarkable and durable response to ICIs despite therapy discontinuation following multiple severe immune-related adverse events (irAEs). Remarkably, the patient remained disease-free for over a year while on prolonged immunosuppression, including high-dose steroids for Guillain-Barré syndrome and risankizumab for ICI-induced psoriasis and psoriatic arthritis. This case suggests the following: (1) durable remission after limited ICI exposure can occur in metastatic SNMM, (2) severe multisystem irAEs may reflect robust antitumour immunity, and (3) biologic immunosuppressants such as IL-23 blockade may effectively control refractory irAEs without apparent compromise of oncologic outcomes. These findings highlight an exceptional therapeutic trajectory and raise new questions about the biology linking irAEs, immunotherapy efficacy and long-term disease control in mucosal melanoma.