LAUSR

We present the first case of simultaneous development of Graves’ disease and type 1 diabetes during anti‐programmed cell death 1 therapy. A 48‐year‐old man with parotid gland adenocarcinoma and lung metastasis had received five courses of nivolumab. Fourteen days after administration of the sixth course, his casual plasma glucose and hemoglobin A1c levels were 379 mg/dL and 7.2%, respectively. Furthermore, thyrotoxicosis was detected with a blood test. Serum total ketone body and thyroid‐stimulating hormone receptor antibody levels increased, and serum C‐peptide level decreased to 0.01 ng/mL thereafter. Thus, we concluded that he simultaneously developed anti‐programmed cell death 1 therapy‐associated type 1 diabetes and Graves’ disease. Among Japanese patients with autoimmune polyglandular syndrome type III, the frequency of human leukocyte antigen‐DRB1*04:05 is higher in those with both type 1 diabetes and Graves’ disease. Our case had human leukocyte antigen‐DRB1*04:05, which might be associated with the simultaneous development of the two diseases.