A 3-year-old boy evaluated for failure to thrive and polyuria has serum potassium 2.4 mEq/L, bicarbonate 32 mEq/L, arterial pH 7.48, urine calcium creatinine ratio elevated, and blood pressure consistently at the 50th percentile. Plasma renin activity is markedly high. What is the most likely diagnosis?

• A Liddle syndrome
• B Primary aldosteronism
• C Distal renal tubular acidosis
• D Antenatal Bartter syndrome ✓

Explanation

Bartter syndrome is a salt wasting tubulopathy from defective ascending limb transport (NKCC2, ROMK or ClC-Kb mutations), producing hypokalemic metabolic alkalosis, hypercalciuria, high renin and aldosterone with normal or low blood pressure. Liddle syndrome and primary aldosteronism both give hypokalemic alkalosis but with hypertension and suppressed renin, which kills those distractors immediately. Distal RTA produces metabolic acidosis, not alkalosis.

Reference: Nelson Textbook of Pediatrics, 21st ed.

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Written and medically reviewed by the StethoPrep medical team.