Nephrogenic DI — RACP Paediatrics MCQ

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HardEndocrineNephrogenic DIRACP Paediatrics

A 2-year-old boy has severe polyuria from infancy. Serum osm 310, urine osm 90. After DDAVP, urine unchanged at 95. Maternal uncles affected. What is the diagnosis?

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Correct answer: A — Nephrogenic DI

Failure to concentrate urine after DDAVP = nephrogenic DI. X-linked AVPR2 mutation (most common genetic cause) fits maternal uncle history. Treatment: hydration, low-solute diet, thiazides.

Reference: RCH Melbourne – 2023 – DI CPG