Fulminant diabetes due to immune checkpoint inhibitors in the emergency department

Immune checkpoint inhibitors (ICIs) are of growing importance in new cancer therapies, exposing patients to various and potentially severe immune-related adverse events and placing emergency physicians on the front line when they occur. If endocrine toxicity is a well-known complication of ICIs, fulminant diabetes with diabetic ketoacidosis is exceptional. We present a case of fulminant diabetes after only two cycles of pembrolizumab in a 53-year-old man with a history of metastatic lung cancer who presented to our emergency department with coma and acidosis revealing diabetic ketoacidosis. The patient was rehydrated and treated with insulin and recovered quickly. Lung toxicity was also suspected on CT-scan findings. This rare and life-threatening complication that developed unusually early during the treatment course may be challenging in a cancer patient. Therefore, emergency physicians should investigate symptoms in patients treated with checkpoint inhibitors and consider toxicity when they present to the ED with complaints compatible with an immune-related adverse event.