Summary

An 84-year-old woman with metastatic squamous cell carcinoma of the nasopharynx and no history of diabetes was started on the antiprogrammed cell death ligand-1 (anti-PD-L1) antibody durvalumab. Four months later, she presented in diabetic ketoacidosis with glucose 488 mg/dL, anion gap 16, positive serum ketones and A_1C9.1%. Antiglutamic acid decarboxylase 65 (GAD) antibody was 13 U/mL (normal, <0.5 U/mL), c-peptide 0.4 ng/dL (normal, 1.1–4.3 ng/mL) and glucose 142 mg/dL. A man with metastatic papillary urothelial carcinoma was treated with the PD-L1 inhibitor atezolizumab. He had no history of diabetes. Nine weeks after initiation, he developed fatigue and polyuria with blood glucose 336 mg/dL, c-peptide 0.6 ng/mL, A_1C8.2% and GAD antibodies 28.4 U/mL (normal, <1 U/mL). Due to the diagnosis of autoimmune diabetes, both patients were treated with insulin. Autoimmune diabetes is a rare immune-related adverse effect of PD-L1 inhibitors. We present the first two cases with documented positive pancreatic autoantibodies.