Autoimmune diabetes mellitus and diabetic ketoacidosis induced by PD-1 inhibitor for gastric adenocarcinoma

The advent of immune checkpoint inhibitors (ICIs) is a revolutionary milestone in the field of immuno-oncology. However, immune-related adverse events should not be ignored. Autoimmune diabetes mellitus, a form of type 1 diabetes mellitus (T1DM), is strongly associated with diabetic ketoacidosis (DKA). As DKA is a life-threat­ening condition, it is important to detect and diagnose it early. This article describes a patient with gastric cancer who developed fulminant diabetes mellitus and DKA after treat­ment with sintilimab. After eight cycles of programmed cell death-1 (PD-1) monoclonal antibody therapy, on day 255 of immunotherapy, the patient developed autoimmune diabetes mellitus and DKA. Laboratory investigations showed extremely high blood glucose levels and metabolic acidosis, and all islet-related autoantibodies were negative. Autoimmune diabetes mellitus, also called immune checkpoint inhibitor-induced T1DM (ICI-T1DM), is a relatively rare complication of ICIs in clinical practice and is often accompanied by DKA. Given the current lack of reliable predictive methods for autoimmune diabetes, regular monitoring of fasting blood glucose is important.