Objective  By summarizing the clinical characteristics and follow-up outcomes of 5 patients with immune checkpoint inhibitor induced diabetes mellitus (ICI-DM) and reviewing the relevant literatures, the article aims at providing reference to clinicians in the diagnosis and treatment of the ICI-DM.

  Methods  Clinical data of 5 patients with ICI-DM who were admitted to Peking Union Medical College Hospital from December 2018 to February 2023 and did retrospectively analyzed.

  Results  Five patients with a mean age of (65±7)years received treatment by the programmed cell death 1 (PD-1) or its ligand inhibitor (PD-L1). The median time from the first immunotherapy to the discovery of elevated plasma glucose was 100 (43, 210)days, and the median cycle of immunotherapy was 7 (2.5, 10.5). The onset of the illness of all the 5 patients started with diabetic ketosis or ketoacidosis. At the onset, urine ketone bodies were positive, random plasma glucose was (36.36±15.89)mmol/L, glycosylated hemoglobin A1c (HbA1c)was (8.6%±0.66%), arterial blood pH was (7.28±0.16), and the median fasting C-peptide level was 0.09 (0.05, 0.32)μg/L. Five patients had an onset plasma glucose level of grade 3 or 4.Then, ICI treatment was discontinued in all patients and insulin therapy started. The daily dosage of insulin was (56±20)IU, supplemented with hypoglycemic drugs. After treatment, urine ketone body turned negative, pH value increased to normal range, and random plasma glucose decreased significantly (the median difference of random blood glucose before and after treatment was 21.30 mmol/L, P=0.043) showing that the treatment was effective. During the follow-up, all patients continued to use insulin. The PD-1 or PD-L1 inhibitors were restarted after hyperglycemia remission. The tumor condition was under control.

  Conclusions  ICI-DM mainly occurs in patients who receive treatment with PD-1 or PD-L1 inhibitors usually with acute hyperglycemia whose laboratory tests indicate insulin secretion defects. Some patients had positive islet cell antibodies, glutamic acid decarboxylase antibodies and autoantibodies.Patients with positive autoantibodies needed early diagnosis and continuous insulin treatment. ICI treatment can be restarted after endocrinologists brought the blood glucose under control.