Abstract
Immune checkpoint inhibitors (ICIs), such as pembrolizumab, have transformed immuno-oncology by demonstrating efficacy against various cancers, including small-cell lung carcinoma and HER2-positive gastric cancer. Despite their benefits, ICIs can provoke immune-related adverse events, with endocrinopathies being rare but carrying significant complications. We report a case of pembrolizumab-induced diabetic ketoacidosis (DKA) in an 87-year-old woman with advanced gastric carcinoma and no prior diabetes history. The patient presented with acute hyperglycemia and metabolic acidosis and was found to have low C-peptide levels without other autoimmune markers typically associated with type 1 diabetes. This case highlights the need for awareness of pembrolizumab as a potential trigger for DKA, especially in patients without a prior diabetes diagnosis. While the management of DKA remains the same, identifying the precipitating factor allows for a comprehensive diagnostic workup and effective long-term management, maintaining the patient's quality of life. This case highlights the complexities of managing DKA in ICI therapy and illustrates the importance of distinguishing between classical DKA presentations and those related to ICIs.