A 3-year-old boy has failure to thrive, polyuria, vomiting, and episodes of dehydration. Investigations show serum potassium 2.4 mEq/L, bicarbonate 34 mEq/L, urine chloride high, plasma renin markedly elevated, aldosterone high, and blood pressure consistently below the 50th percentile. Urine calcium to creatinine ratio is elevated. What is the most likely diagnosis?

• A Primary hyperaldosteronism
• B Gitelman syndrome
• C Distal renal tubular acidosis
• D Antenatal Bartter syndrome ✓

Explanation

Bartter syndrome mimics loop diuretic effect: defective salt reabsorption in the thick ascending limb causes hypokalemic metabolic alkalosis, high renin and aldosterone, normal to low blood pressure, and hypercalciuria. Primary hyperaldosteronism is excluded by low rather than high renin, Gitelman syndrome occurs later with hypocalciuria and hypomagnesemia, and distal RTA produces metabolic acidosis rather than alkalosis.

Reference: Nelson Textbook of Pediatrics, 21st ed.

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