A Rare Case of Severe Diabetic Ketoacidosis in a Patient With Metastatic Renal Cell Carcinoma Being Treated With Nivolumab.

Immune checkpoint inhibitors are becoming of more use as clinicians are prescribing them for patients with different malignancies. As their use continues to increase, clinicians must be aware of the side effects, which are autoimmune in nature. Autoimmune diabetes has been described in the past while patients were being treated with programmed cell death protein 1 (PD-1) inhibitors, but it usually occurs after the patient's fourth or fifth cycle. In this case presentation, we describe a patient with no history of type 1 or 2 diabetes presenting to the emergency department with severe diabetic ketoacidosis. At the time of presentation, he was on his 22nd cycle of nivolumab for metastatic renal cell carcinoma. The patient was eventually treated successfully, but upon discharge, he was prescribed a large dose of insulin regimen to control his blood sugar levels at home. We attributed his new diagnosis of insulin-dependent diabetes to the PD-1 inhibitor nivolumab.