Fulminant Type 1 Diabetes Mellitus Leading to Diabetic Ketoacidosis and Mesenteric Ischemia With Necrosis Following Pembrolizumab Administration: A Case Report.

Immune checkpoint inhibitors (ICIs), such as pembrolizumab, have revolutionized cancer therapy but can lead to severe immune-related adverse events (irAEs). We present a case of fulminant type 1 diabetes mellitus (T1DM) with diabetic ketoacidosis (DKA) and mesenteric ischemia in a 78-year-old woman with recurrent stage IIIC1 cervical cancer treated with pembrolizumab. Thirty-four days after initiating a pembrolizumab-containing regimen, she presented with vomiting, severe hyperglycemia, metabolic acidosis, and strongly positive urine ketones. Laboratory findings confirmed complete insulin deficiency, leading to a diagnosis of fulminant T1DM and DKA, requiring intensive insulin therapy. Despite treatment, her condition rapidly deteriorated, with worsening DKA, hyperglycemia, gastrointestinal bleeding, and extensive mucosal necrosis identified through endoscopy and imaging. The patient ultimately progressed to septic shock and died the same day. Fulminant T1DM is characterized by abrupt β-cell destruction and rapid DKA onset. In this case, DKA likely contributed to mesenteric ischemia, a severe vascular complication. This is the first reported case of fulminant T1DM, DKA, and mesenteric ischemia following pembrolizumab. The case underscores the importance of vigilance, early recognition, and multidisciplinary management of irAEs to prevent fatal outcomes.