Abstract
The patient, a woman in her 60s, was undergoing treatment with an anti-PD-1 antibody, an immune checkpoint inhibitor （ICI）, to address lung metastases following hard palate cancer resection. Four years after initiating treatment, during a visit to an otorhinolaryngologist, her HbA1c levels were found to be slightly elevated without any precipitating factors. Five days after referral to the endocrinology department, the patient exhibited hyperglycemic symptoms and ketosis. We ultimately diagnosed fulminant type 1 diabetes. Immune-related adverse events （irAEs） due to ICI usage manifest throughout the body, including the skin, lungs, and endocrine organs. Fulminant type 1 diabetes triggered by irAEs progresses with alarming rapidity and poses a significant mortality risk unless diagnosed and treated with insulin expeditiously. Although irAEs are closely monitored following ICI administration, patients are frequently misdiagnosed with incidental hyperglycemia and managed as type 2 diabetes. In this case, an irAE was detected due to a slight increase in HbA1c during a routine examination prompted the consideration of an irAE, leading to a swift referral to a specialist department. Consequently, treatment was initiated before symptoms became severe, allowing the early resumption of the appropriate therapy for the primary disease.
