Fulminant Type 1 Diabetes Induced by Immune Checkpoint Inhibitors in a Patient with Autoimmune Predisposition.

We report a case of fulminant type 1 diabetes in a 73-year-old woman who was treated with nivolumab and ipilimumab for plantar malignant melanoma. Despite carrying the protective HLA-DRB1*15:01-DQB1*06:02 haplotype, she developed marked hyperglycemia (596 mg/dL), ketoacidosis, anti-glutamic acid decarboxylase (GAD) antibody positivity, HbA1c 6.6%, and low urinary C-peptide (1.0 μg/day). The detection of anti-GAD antibodies suggests an underlying autoimmune predisposition, which is likely aggravated by immune checkpoint inhibitors. Her history of Graves' disease and familial autoimmunity further supports this predisposition. This case highlights the importance of monitoring endocrine immune-related adverse events in patients with autoimmune backgrounds.