Tislelizumab-induced fulminant type 1 diabetes mellitus (FT1D): A case report and literature review.

rationaleImmune checkpoint inhibitors, such as tislelizumab, are widely used in oncology but can cause serious immune-related adverse events. Endocrine disorders are common, with fulminant type 1 diabetes mellitus (FT1D) being a rare but life-threatening complication. This case highlights the rapid onset of FT1D following tislelizumab therapy. PATIENT CONCERNS: An elderly male with lung squamous cell carcinoma, with no prior history of diabetes, was admitted to the hospital complaining of systemic malaise, nausea, and vomiting. DIAGNOSIS: Laboratory findings confirmed diabetic ketoacidosis (DKA), hyperkalemia, and hyponatremia. Further assessment revealed severely depleted C-peptide levels (both fasting and postprandial <0.05 ng/mL) and an HbA1c of 7.7%, with negative islet autoantibodies. A diagnosis of tislelizumab-induced fulminant type 1 diabetes mellitus was established.

interventionsThe patient was managed for DKA with fluid resuscitation, continuous intravenous insulin infusion, and electrolyte correction. OUTCOMES: The patient's metabolic abnormalities were corrected, and his blood glucose levels stabilized under the subcutaneous insulin regimen. LESSONS: Tislelizumab can induce FT1D, which presents acutely and can be fatal. This case underscores the critical need for vigilant and regular blood glucose monitoring in patients receiving immune checkpoint inhibitors. Enhanced patient education on the symptoms of hyperglycemia is essential to enable early detection and prompt intervention, thereby preventing severe complications such asDKA.