Diabetic ketoacidosis induced by a single dose of pembrolizumab

Immune checkpoint inhibitors are a new class of anticancer drugs recently approved by the US Food and Drug Administration (FDA) for the treatment of various malignancies. Pembrolizumab is an immune checkpoint inhibitor that targets the programmed cell death protein-1 (PD-1) receptor and blocks its interaction with programmed cell death ligand-1 (PD-L1) and programmed cell death ligand-2 (PD-L2). Pembrolizumab was first approved by the FDA in 2014 for the treatment of advanced melanoma and is currently approved for use in non-small cell lung cancer and several other neoplasms. Immune checkpoint inhibitors such as pembrolizumab have been reported to induce immune-mediated side effects, including type 1 diabetes mellitus in very rare cases (0.1% in clinical trials). Here, we report the case of a woman with no known history of diabetes who presented to our emergency department in a state of diabetic ketoacidosis within 3 weeks of receiving only a single dose of pembrolizumab therapy, and without any previous exposure to immunotherapy. This case of abrupt adult-onset type 1 diabetes mellitus is an example of the undesirable side effects that can emerge after only a brief exposure to an immune checkpoint inhibitor. Close monitoring of patients receiving immune checkpoint inhibitors is warranted for the early diagnosis and management of imminent and potentially life-threatening complications.