Abstract
Pembrolizumab, a monoclonal antibody against programmed cell death-1 receptor, was licensed for advanced cancers. Although the use of pembrolizumab can enhance the effect of cancer treatment, it can increase immune-related adverse events. We describe an elderly woman who developed ketoacidosis after receiving pembrolizumab to treat metastatic melanoma. In the presentation, laboratory analysis showed that hyperglycemia and anion gap metabolic acidosis was consistent with diabetic ketoacidosis. Except for pembrolizumab, no other predisposing factors were found. The blood glucose levels before using pembrolizumab were normal. The patient responded well to intravenous fluids, insulin therapy, and treatment to correct electrolyte disturbances. She was diagnosed with severe diabetic ketoacidosis (DKA) because of new-onset diabetes mellitus which associated with pembrolizumab therapy. Two months after she was discharged from the hospital, she continued to take insulin as well as metformin to treat her diabetes. Clinicians need to be alert about diabetes mellitus and ketoacidosis for patients undergoing pembrolizumab treatment.