A 19-year-old man is evaluated for severe hypertension (BP 178/104 mmHg) and hypokalaemia (K 2.4 mEq/L) with metabolic alkalosis. Plasma renin activity is undetectable and plasma aldosterone is 2 ng/dL (suppressed). His father had similar findings and died young of a stroke. Genetic testing shows a mutation in SCNN1B. Which drug will correct both the hypertension and hypokalaemia?
- A Spironolactone
- B Amiloride ✓
- C Hydrochlorothiazide
- D Captopril
Correct answer: B. Amiloride
Explanation
Liddle syndrome is caused by gain-of-function mutations in the beta or gamma subunits of the epithelial sodium channel (SCNN1A or SCNN1G), producing constitutive ENaC activity in the collecting duct. Sodium retention causes hypertension and potassium wasting, while mineralocorticoid receptors are unstimulated, so renin and aldosterone are both suppressed. Amiloride directly blocks ENaC and corrects the entire phenotype. Spironolactone fails because the channel is active independent of aldosterone, and captopril cannot suppress renin further below zero.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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