Immune checkpoint inhibitor-related pancreatitis with fulminant type 1 diabetes mellitus: a case report

Immune checkpoint inhibitors (ICIs) are widely used in tumor therapy, and the immune-related adverse events (irAEs) they induce can involve multiple organs. As an organ with both endocrine and exocrine functions, pancreatic involvement may manifest as acute pancreatitis, new-onset diabetes mellitus, or even a combination of both. Among these, ICI-induced acute pancreatitis concurrent with fulminant type 1 diabetes mellitus (FT1DM) is extremely rare but highly critical and easily missed in clinical practice.

A 59-year-old male patient with squamous cell carcinoma of the left base of the tongue received toripalimab combined with chemotherapy. On day 7 after treatment, he presented with nausea, vomiting, and altered mental status. Emergency examination revealed hyperglycemia (17.4 mmol/L), severe diabetic ketoacidosis (blood ketones 9.52 mmol/L, pH 7.28), and significantly elevated serum amylase (370 U/L). Abdominal CT showed swelling of the body and tail of the pancreas with surrounding exudation, consistent with acute pancreatitis. His glycated hemoglobin (HbA1c) was normal (5.4%), pancreatic autoantibodies were negative, and islet function was completely lost. He was diagnosed with toripalimab-associated acute pancreatitis (Grade 3) concurrent with FT1DM. ICIs were permanently discontinued immediately. The patient was treated with fasting, fluid replacement, somatostatin to inhibit pancreatic enzyme secretion, and intensive insulin pump therapy for glycemic control. Glucocorticoids were not administered. After 11 days of comprehensive treatment, his symptoms resolved, and he was discharged upon normalization of pancreatic enzymes and blood glucose levels.

PD-1 inhibitors can simultaneously impair both the endocrine and exocrine functions of the pancreas, leading to the coexistence of acute pancreatitis and FT1DM. Clinicians must maintain a high index of suspicion for this dual injury. For patients receiving ICI therapy, emergency evaluation of pancreatic function is warranted once gastrointestinal symptoms or unexplained hyperglycemia/ketosis occur. Early drug withdrawal and individualized management centered on supportive care can effectively prevent life-threatening complications. Notably, this case represents the first report of such dual pancreatic injury in a patient with locally advanced tongue base squamous cell carcinoma receiving first-cycle toripalimab combined with paclitaxel plus cisplatin chemoimmunotherapy, with distinct atypical clinical manifestations and a faster steroid-free recovery trajectory compared with the single previously published toripalimab-associated case.