MCQ: Recurrent Weakness

Correct Answer: A. Bartter syndrome

Explanation

Bartter syndrome is an inherited renal salt-wasting tubulopathy caused by impaired sodium, potassium, and chloride reabsorption, primarily involving the thick ascending limb of the loop of Henle. Its physiology resembles the effect of chronic loop diuretic therapy.

Typical findings include:

• Hypokalemia
• Hypochloremic metabolic alkalosis
• Normal or low blood pressure
• Renal salt wasting with increased renin and aldosterone
• Polyuria and polydipsia
• Growth failure
• Hypercalciuria and nephrocalcinosis, particularly in antenatal/infantile forms
• Variable urinary calcium excretion in some later-onset forms

Why the other options are incorrect

A. Bartter syndrome
Correct. Hypokalemic metabolic alkalosis with renal salt wasting, normal/low blood pressure, and hypercalciuria strongly suggests Bartter syndrome.

B. Gitelman syndrome
Usually presents later, often in adolescence, with hypokalemic metabolic alkalosis, hypomagnesemia, and hypocalciuria.

C. Liddle syndrome
Causes hypertension, hypokalemia, and metabolic alkalosis because of increased ENaC activity. The absence of hypertension argues against it.

D. Primary hyperaldosteronism
Typically produces hypertension with hypokalemia and metabolic alkalosis.

E. Renal tubular acidosis
Produces metabolic acidosis, rather than the metabolic alkalosis characteristic of Bartter and Gitelman syndromes.

High-Yield Exam Pearls

• Bartter = loop diuretic-like disorder → think hypokalemic metabolic alkalosis + hypercalciuria.
• Gitelman = thiazide-like disorder → think hypokalemic metabolic alkalosis + hypomagnesemia + hypocalciuria.
• Hypertension + hypokalemic metabolic alkalosis → think Liddle syndrome or mineralocorticoid excess, rather than Bartter/Gitelman.
• Bartter → high renin + high aldosterone, but blood pressure remains normal or low because of renal salt wasting.
• Antenatal/infantile Bartter may present with maternal polyhydramnios, prematurity, severe polyuria, dehydration, hypercalciuria, and nephrocalcinosis.
• Bartter type IV is an important exam association with sensorineural deafness.
• Bartter type III can resemble Gitelman syndrome, so urinary calcium and magnesium are useful clues rather than absolute rules.
• Metabolic alkalosis is the key acid–base clue: Bartter/Gitelman → alkalosis; renal tubular acidosis → acidosis.

You can also practice another MCQ on Hyperammonemia

Reference

Orphanet. Bartter syndrome [Internet]. Paris: Orphanet; [cited 2026 Sep 22].