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irAE Diabetes Insipidus — SCE Medical Oncology MCQ

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HardImmunotherapy & Targeted TherapyirAE Diabetes InsipidusSCE Medical Oncology

A 55-year-old woman with metastatic melanoma on pembrolizumab develops new-onset diabetes insipidus (polyuria 8L/day, serum osmolality 310, urine osmolality 95). MRI pituitary shows thickened pituitary stalk with loss of posterior pituitary bright spot. What is the diagnosis and management?

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Correct answer: C — Immune-related central diabetes insipidus

Immune-related central diabetes insipidus from posterior pituitary/stalk hypophysitis is a rare but recognised irAE. MRI findings of pituitary stalk thickening and loss of posterior bright spot are characteristic. Management includes desmopressin (DDAVP) for DI, and assessment of anterior pituitary function (ACTH, TSH, LH/FSH, prolactin). Unlike anterior hypophysitis (which often becomes permanent), posterior pituitary function may recover. Hold ICI during acute management and consider high-dose steroids.

Reference: https://www.nice.org.uk/guidance/conditions-and-diseases/cancer