Liddle Syndrome

What happens in Liddle syndrome

In the kidney's collecting ducts, ENaC channels reabsorb sodium from urine back into the blood, and potassium is excreted in exchange. Normally, aldosterone turns these channels up or down, and the channels are regularly removed from the cell surface.

In Liddle syndrome, gene variants prevent the channels from being removed, so they stay active. The kidney keeps reabsorbing sodium and water regardless of the body's needs, which:

• expands blood volume and raises blood pressure
• increases potassium loss in urine, causing low blood potassium (hypokalemia)
• causes metabolic alkalosis
• suppresses renin and aldosterone through feedback

Symptoms

Many people have no symptoms apart from high blood pressure, found on routine checks. When present, symptoms include:

• headaches
• tiredness
• muscle weakness or cramps, from low potassium
• palpitations
• increased urination and thirst

Long-standing uncontrolled hypertension can cause:

• thickening of the heart muscle and heart failure
• stroke, sometimes at a young age
• kidney damage

The severity varies, even within the same family. Not everyone has low potassium.

Liddle syndrome vs similar conditions

Diagnosis

Doctors suspect Liddle syndrome in young people with high blood pressure, especially with low potassium or a family history. Tests include:

• blood pressure measurement and checks for organ damage
• potassium, bicarbonate and kidney function
• plasma renin and aldosterone: both low in Liddle syndrome
• urine potassium and sodium
• genetic testing for SCNN1A, SCNN1B and SCNN1G variants, which confirms the diagnosis
• trial response to amiloride may support the diagnosis

Treatment

• amiloride or triamterene: these potassium-sparing diuretics directly block the ENaC channel, lowering blood pressure and normalizing potassium
• low-sodium diet: essential to the effect of treatment
• monitoring: regular blood pressure and potassium checks, since potassium can rise too high, especially with kidney disease or other medicines
• other blood pressure medicines may be added if needed
• spironolactone and eplerenone are ineffective because aldosterone is not the cause

Kidney transplantation has corrected the disorder in rare cases of kidney failure, since the new kidney carries normal channels.

Family screening

Because inheritance is autosomal dominant, first-degree relatives should have blood pressure and potassium checks and be offered genetic testing once a family variant is known. Early diagnosis allows treatment before organ damage develops.

Outlook

With correct diagnosis and treatment, blood pressure is usually well controlled and the outlook is excellent. Undiagnosed Liddle syndrome can lead to early stroke, heart disease and kidney damage.

Frequently asked questions

What is Liddle syndrome?

Liddle syndrome is a rare inherited condition in which a kidney sodium channel is overactive, so the body retains too much salt and water. This causes early-onset high blood pressure, often with low potassium and low renin and aldosterone levels.

What are the symptoms of Liddle syndrome?

Many people only have high blood pressure, often found in childhood or early adulthood. Low potassium can cause muscle weakness, cramps, tiredness, palpitations and increased urination. Untreated, it can lead to stroke and heart or kidney damage.

How is Liddle syndrome inherited?

It is autosomal dominant: one copy of the altered gene from either parent is enough. Each child of an affected parent has a 50% chance of inheriting it. Rarely, it arises as a new mutation.

What is the treatment for Liddle syndrome?

Amiloride or triamterene, which block the overactive sodium channel, plus a low-salt diet. These usually control blood pressure and correct low potassium. Spironolactone does not work because aldosterone is not the cause.

How is Liddle syndrome different from hyperaldosteronism?

Both cause high blood pressure and low potassium, but in hyperaldosteronism aldosterone levels are high and spironolactone works. In Liddle syndrome, aldosterone is low, and only ENaC blockers such as amiloride are effective.