Liddle syndrome

What it is, symptoms and effects

From: MedlinePlus Genetics, National Library of Medicine

Liddle syndrome is an inherited form of high blood pressure (hypertension). This condition is characterized by severe hypertension that begins unusually early in life, often in childhood, although some affected individuals are not diagnosed until adulthood. Some people with Liddle syndrome have no additional signs or symptoms, especially in childhood. Over time, however, untreated hypertension can lead to heart disease or stroke, which may be fatal.

In addition to hypertension, affected individuals can have low levels of potassium in the blood (hypokalemia). Signs and symptoms of hypokalemia include muscle weakness or pain, fatigue, constipation, or heart palpitations. The shortage of potassium can also raise the pH of the blood, a condition known as metabolic alkalosis.

Causes and biological mechanisms

From: MedlinePlus Genetics, National Library of Medicine

Liddle syndrome is caused by mutations in the SCNN1B or SCNN1G gene. Each of these genes provides instructions for making a piece (subunit) of a protein complex called the epithelial sodium channel (ENaC). These channels are found at the surface of certain cells called epithelial cells in many tissues of the body, including the kidneys, where the channels transport sodium into cells.

In the kidney, ENaC channels open in response to signals that sodium levels in the blood are too low, which allows sodium to flow into cells. From the kidney cells, this sodium is returned to the bloodstream (a process called reabsorption) rather than being removed from the body in urine.

Mutations in the SCNN1B or SCNN1G gene change the structure of the respective ENaC subunit. The changes alter a region of the subunit that is involved in signaling for its breakdown (degradation) when it is no longer needed. As a result of the mutations, the subunit proteins are not degraded, and more ENaC channels remain at the cell surface. The increase in channels at the cell surface abnormally increases the reabsorption of sodium (followed by water), which leads to hypertension. Reabsorption of sodium into the blood is linked with removal of potassium from the blood, so excess sodium reabsorption leads to hypokalemia.

Inheritance and family implications

From: MedlinePlus Genetics, National Library of Medicine

This condition is inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the disorder.

How common is it?

From: MedlinePlus Genetics, National Library of Medicine

Liddle syndrome is a rare condition, although its prevalence is unknown. The condition has been found in populations worldwide.

Reported clinical features and what the terms mean

The following findings are associated with this condition in Orphanet. They are not a checklist for diagnosing yourself, and they do not all occur in every affected person. Some are examination, imaging or laboratory findings that cannot be recognised at home.

The frequency labels describe how often a finding was reported among people with the condition in the source. They do not give the chance that a person with that symptom has the condition. Definitions below reproduce HPO terminology; they explain the term, not the likely severity in an individual.

Arrhythmia · Very frequent (99-80%)

Any cardiac rhythm other than the normal sinus rhythm. Such a rhythm may be either of sinus or ectopic origin and either regular or irregular. An arrhythmia may be due to a disturbance in impulse formation or conduction or both.

Constipation · Very frequent (99-80%)

Infrequent or difficult evacuation of feces.

Hypertension · Very frequent (99-80%)

The presence of chronic increased pressure in the systemic arterial system.

Hypokalemia · Very frequent (99-80%)

The concentration of potassium(1+) in the blood circulation is below the lower limit of normal.

Cerebral ischemia · Frequent (79-30%)

Restriction of arterial blood supply to the brain associated with insufficient oxygenation to support the metabolic requirements of the tissue.

Fatigue · Frequent (79-30%)

A subjective feeling of tiredness characterized by a lack of energy and motivation.

Muscle weakness · Frequent (79-30%)

Reduced strength of muscles.

Nephropathy · Frequent (79-30%)

A nonspecific term referring to disease or damage of the kidneys.

Renal insufficiency · Frequent (79-30%)

A reduction in the level of performance of the kidneys in areas of function comprising the concentration of urine, removal of wastes, the maintenance of electrolyte balance, homeostasis of blood pressure, and calcium metabolism.

Which doctor should you see?

The suggested department for discussing Liddle syndrome is Nephrology, with a nephrologist as the relevant type of clinician. General physician / Family Medicine; paediatrician for children. Referral depends on symptoms.

Additional services that may be relevant, depending on the findings, include: Clinical Genetics.

This is an editorial referral starting point. The appropriate clinic depends on the person’s age, symptoms, previous diagnosis and local services. The first clinician can decide whether another specialty or a team is needed; a department label does not confirm the diagnosis.

How to prepare for an assessment

Bring a short timeline of the main symptoms: when they first appeared, whether they are constant or episodic, what seems to change them, and how they affect daily activities. Include previous reports, discharge summaries, current medicines and supplements, allergies, and any relevant family history. A dated record is more useful than trying to match every feature in an online article.

Ask the clinician what is already established and what remains uncertain. If a test is suggested, ask what question it answers, what its limitations are and how the result would change the next step. The information here is not an instruction to arrange every possible test. In children, bring growth, developmental and school information if it is relevant to the concern.

• How is kidney function being assessed over time?
• Are any current medicines or supplements relevant to kidney safety?
• Is there an individual recommendation about fluids, diet or blood pressure?

Treatment discussions and follow-up

Where the source describes treatments, these are an overview of possible care, not a prescription for an individual. Ask which option applies to the confirmed diagnosis, what benefit is expected, what adverse effects to watch for and how progress will be assessed. Availability, approvals and local practice can differ from the country described in the source.

Before leaving the appointment, clarify the next review date, who will communicate results, and whom to contact if the situation changes. Discuss difficulties with sleep, work, school, mobility, eating or emotional wellbeing when these are relevant. Practical support may require coordination between the treating clinician and other services.

The collected references do not establish a complete prevention or long-term outlook section for this entry. Missing information should not be interpreted as proof that prevention is impossible or that a particular outcome is inevitable. Ask what is known for the exact subtype, stage and personal circumstances, and which uncertainties remain.

When to seek emergency help

Severe breathing difficulty, collapse, new stroke-like symptoms, a seizure that is prolonged or repeated without recovery, uncontrolled major bleeding, or an immediate risk of self-harm require emergency help. In India, call 112 or reach the nearest emergency department. This is a general, non-exhaustive warning list; it is not a condition-specific triage tool.