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ICI-Induced Type 1 Diabetes — RACP Adult Medicine MCQ

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HardEndocrinology & DiabetesICI-Induced Type 1 DiabetesRACP Adult Medicine

A 72-year-old man with metastatic renal cell carcinoma on nivolumab develops acute onset polyuria, polydipsia, and fatigue. His blood glucose is 32 mmol/L and blood ketones are 6.2 mmol/L. HbA1c is 40 mmol/mol. Anti-GAD and anti-IA2 antibodies are positive. What is the most likely cause?

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Correct answer: A — Immune checkpoint inhibitor-induced type 1 diabetes

Immune checkpoint inhibitors (ICIs) such as nivolumab can cause autoimmune destruction of pancreatic beta cells, resulting in fulminant type 1 diabetes with DKA. This is an immune-related adverse event (irAE). The normal HbA1c with new DKA and positive islet antibodies confirms new-onset autoimmune diabetes. Management includes insulin therapy. The ICI may need to be permanently discontinued depending on severity. Endocrinology consultation is essential.

Reference: eTG – 2025 – Endocrinology; ASCO – 2021 – irAE Management Guidelines