Combined Application of Nivolumab and Intravesical Bacillus Calmette-Guérin Led to Acute-Onset Type 1 Diabetes.

We report a case of acute-onset type 1 diabetes due to combined application of nivolumab and intravesical Bacillus Calmette-Guérin (BCG). An 84-year-old woman underwent lung resection for pulmonary squamous cell carcinoma. She had been treated for type 2 diabetes and later experienced lung cancer recurrence. She was started on nivolumab treatment, and complete response was achieved for one year. However, during this time, she was diagnosed with superficial bladder cancer and underwent surgery but experienced recurrence. After one month of intravesical BCG instillation, the patient developed acute-onset type 1 diabetes. Thus, we recommend that combined application of nivolumab and intravesical BCG be avoided.