Liddle syndrome is characterized by
**Core Concept**
Liddle syndrome is a rare genetic disorder characterized by primary aldosteronism, hypertension, and hypokalemia. It is caused by mutations in the genes encoding the epithelial sodium channel (ENaC), leading to excessive sodium reabsorption in the collecting duct of the kidney.
**Why the Correct Answer is Right**
The mutations in ENaC increase the channel's activity, resulting in increased sodium reabsorption. This leads to increased aldosterone secretion, which in turn causes hypertension and hypokalemia. The increased sodium reabsorption also leads to water retention, contributing to hypertension. The excessive sodium absorption is thought to be due to the gain-of-function mutations in the ENaC subunits, which make the channel overly sensitive to aldosterone.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because Liddle syndrome is not characterized by hyperaldosteronism due to an adrenal tumor.
**Option B:** This option is incorrect because Liddle syndrome is not caused by mutations in the gene encoding the renin-angiotensin system.
**Option C:** This option is incorrect because Liddle syndrome is not characterized by hypokalemia due to a defect in the sodium-potassium pump.
**Clinical Pearl / High-Yield Fact**
Liddle syndrome is a rare cause of primary aldosteronism, and its diagnosis is often delayed due to its similarity to other causes of hypertension and hypokalemia.
**Correct Answer:** D.