LAUSR

Abstract Rationale: Sintilimab is a novel programmed cell death receptor-1 (PD-1) inhibitor approved in the treatment of classical Hodgkin's lymphoma and undergoing clinical trials for various malignancies. As a PD-1 inhibitor, sintilimab is known to cause autoimmune adverse events similar to other PD-1 inhibitors. Diabetic ketoacidosis (DKA) is a rare but severe adverse event of this therapy. Patient concerns: We report a case of a 59-year-old man who developed DKA after 5 doses of sintilimab for small cell lung cancer. His fasting glycemia level was 14.07 mmol/L, urine ketone bodies were 4+, arterial blood pH was 7.271, bicarbonate was 12.3 mmol/L, and glycated hemoglobin (HbA1c) was 7.4%. Extended investigations revealed that fasting C-peptide was undetectable (<0.003 nmol/L). Diagnosis: These laboratory investigations supported the diagnosis of fulminant type 1 diabetes mellitus, but no β-cell related antibodies were positive. Interventions: After remission of DKA, he was treated with insulin therapy to acquire a normalization of glycemia and the disappearance of symptoms. Outcomes: Sintilimab was withheld after 6 cycles and was converted to durvalumab to sustain the therapeutic effect. Lessons: This case and associated literature review illustrate the importance of educating and monitoring patients who start PD-1 inhibitor therapy regarding this potentially life-threatening complication.