Diabetes Mellitus Secondary to Treatment with Immune Checkpoint Inhibitors

Cancer immunotherapy has been one of the highlights in the advancement of cancer care. Certain immune checkpoint inhibitors bind to PD-1 on T cells and mediate an antitumour immune response. Given that immune checkpoint inhibitors are becoming part of standard care, a new class of adverse events—immune-related adverse events—has emerged. Among them is endocrine toxicity, most commonly targeting the thyroid, pituitary, or adrenal glands. New-onset diabetes mellitus has been reported in fewer than 1% of patients. We present a patient with type 1 diabetes mellitus secondary to immunotherapy, together with an overview of the associated literature. Patients who develop type 1 diabetes mellitus experience a rapid course, and diabetic ketoacidosis is commonly the presenting symptom. Insulin is currently the treatment of choice; oral antidiabetics or corticosteroids do not assist in management. Several predictive factors are under investigation, but physician awareness and prompt management are key to a positive outcome.