Autoimmune polyendocrine syndrome type 3, characterized by autoimmune thyroid disease, type 1 diabetes mellitus, and isolated ACTH deficiency, developed during adjuvant nivolumab treatment.

Autoimmune polyendocrine syndrome (APS) is one of the life-threatening immune-related adverse events (irAEs). We firstly report a case of APS induced by adjuvant nivolumab therapy. Clinicians should be aware of the potential risks of developing severe irAEs when applying adjuvant immunotherapy.