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Bartter Type III CLCNKB — ESENeph MCQ

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HardTubular DisordersBartter Type III CLCNKBESENeph

A 35-year-old woman with Bartter syndrome type III (CLCNKB mutation) presents with hypokalaemia (K+ 2.4 mmol/L), metabolic alkalosis, normal blood pressure, and elevated renin and aldosterone. She is normocalciuric (distinguishing from Gitelman). What is the defective transporter?

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Correct answer: C — ClC-Kb (chloride channel in thick ascending limb and distal convoluted tubule)

Bartter syndrome type III is caused by mutations in CLCNKB encoding the ClC-Kb chloride channel, which is expressed in both the thick ascending limb and the distal convoluted tubule. Type I involves NKCC2 (SLC12A1); Type II involves ROMK (KCNJ1); Type IV involves Barttin (BSND) or combined CLCNKA+CLCNKB. Type III typically presents in later childhood/adolescence and may overlap clinically with Gitelman syndrome. Normocalciuria distinguishes it from Gitelman (which has hypocalciuria). Treatment includes potassium supplementation, NSAIDs (Indometacin), and potassium-sparing diuretics.

Reference: https://guidelines.ukkidney.org