Introduction

Bartter syndrome refers to a group of rare genetic disorders characterised by defects in kidney function. As a result, the kidney is unable to reabsorb salt, which is then excreted from the body. This leads to an imbalance of fluid and electrolytes in the body. Potassium, calcium, magnesium, sodium, and chloride are the most commonly affected electrolytes.

The classification system for these genetic disorders is based on the mutations in specific genes. Antenatal (before birth) Bartter syndrome is usually present before birth and includes Types 1, 2, 4a, and 4b. It is a rare autosomal recessive renal tubular disorder. Bartter syndrome Type 3 is also called classic Bartter syndrome. Gitelman syndrome shows considerable overlap with Bartter syndrome, particularly Type 3, and is occasionally categorised under Bartter syndrome.¹

Epidemiology

Bartter syndrome can affect males and females equally, affecting approximately 1 in 100,000 people in the general population. However, the exact prevalence cannot be estimated as many cases go undiagnosed or misdiagnosed. There is no data that it affects people of any race or ethnicity. ^{1 2}

Importance of effective management and treatment

It is important to understand the complex mechanisms behind the development of this disease because it can cause many health problems thus affecting quality of life. The condition requires special treatment approaches in order to avoid long-term complications.

Pathophysiology

Bartter syndrome affects genes that encode various proteins essential for proper kidney function. Kidney functions include maintaining a fluid balance and concentration of different electrolytes through reabsorption. These electrolytes are important for performing various functions of the body and are required for various biochemical reactions. 

However, the functioning of the kidneys, such as the transport of electrolytes into the bloodstream, is disturbed by mutations occurring in Bartter syndrome. This abnormal functioning prevents the reabsorption of sodium and chloride ions from urine. This causes ions to be lost through urine.. Other electrolytes, such as potassium, magnesium, and calcium, are also affected, disrupting the proper balance of electrolytes in the body, ultimately leading to specific symptoms.^{1 2}

Clinical manifestations

Symptoms include the following:

• Polyuria
• Polydipsia
• Tendency for volume depletion
• Salt craving
• Constipation
• Electrolyte imbalance
• Vomiting
• Failure to thrive
• Stunted growth 

Symptoms appearing in late childhood include:

• Cramps
• Fatigue
• Muscle weakness
• Developmental delay
•  Minimal brain dysfunction
• Nonspecific electroencephalographic changes^{3 4}

Diagnostic approaches

Diagnosis is made through history and physical exam, along with specific laboratory abnormalities. 

• Bartter syndrome is characterised by electrolyte and acid-base abnormalities, including hypokalemia and metabolic alkalosis in nearly all cases 
• Abdominal radiographs, intravenous pyelograms (IVPs), renal ultrasonograms, or spiral CT scans can be used to document nephrocalcinosis 
• Genetic testing can be considered to identify specific mutations²

Differential diagnosis

Differential diagnosis refers to distinguishing the disease from other similar conditions. Some of the conditions to consider in the differential diagnosis of Bartter syndrome include the following:

• Diuretic abuse
• Gitelman syndrome
• Hypokalemia
• Hypochloremic alkalosis
• Hyperprostaglandin E syndrome
• Familial hypomagnesemia with hypercalciuria/nephrocalcinosis
• Activating mutations of the CaSR calcium-sensing receptor³

Treatment strategies

Pharmacological interventions

• Potassium-sparing diuretics
• ACE inhibitors
• Magnesium and potassium supplements

Dietary modifications

• Nutritional requirements
• Fluid and electrolyte management

Monitoring and follow-up

• Regular laboratory tests
• Growth and development tracking

Management 

Diet and physical activity

Diet

To prevent hypovolemia, a balanced diet is required in Bartter syndrome along with adequate salt and water intake. Potassium levels should be maintained to replace urinary potassium losses. Tomatoes, bananas and orange juice have a high potassium content.

Adequate protein and calorie intake is also important for a person with stunted growth. The role of other dietary supplements (e.g., citrate, magnesium, vitamins) is not well established.

Activity

You can perform your normal life activities with Bartter syndrome. However, care should be taken to avoid dehydration during exercise. Dehydration could also lead to electrolyte imbalance, which further contributes to the symptoms of the disease. Cardiac abnormalities due to potassium imbalance can also occur.

Pharmacological treatment

Treatment for Bartter syndrome focuses on addressing the specific symptoms present in each individual and often requires the coordinated efforts of a team of specialists. This team may include paediatricians or general internists, nephrologists (including pediatric nephrologists), and other healthcare professionals who systematically and comprehensively plan the patient's treatment. While there is no cure for these disorders, lifelong administration of certain supplements and medications is necessary.

Supplementations 

Restoring the body's natural fluid and electrolyte balance is the cornerstone of treatment. Typically, this involves potassium and sodium chloride supplements to address electrolyte imbalances. Due to corresponding chloride deficits, potassium chloride supplementation is favoured over other types of potassium salts. Muscle spasms or tetany may be treated with magnesium supplements, particularly in cases of Bartter syndrome Type 3.

NSAIDs

Increased levels of prostaglandins worsen the polyuria and electrolyte abnormalities. Treatment includes a drug that decreases the production of prostaglandins, such as ibuprofen, indomethacin, or celecoxib. Indomethacin is usually given in Bartter syndrome, but it can have severe side effects. Indomethacin causes gastric and intestinal perforations, especially in premature babies. It is recommended to use these drugs in combination with an antacid or stomach acid blockers. Newer NSAIDs (COX2 inhibitors) are also effective in treating Bartter syndrome. These agents have a much lower risk of intestinal side effects. Long-term use of NSIADs may adversely affect kidney function.

Diuretics 

Potassium-sparing diuretics such as spironolactone or amiloride are also given to some individuals. These drugs retain potassium and acid and excrete sodium in urine, improving low potassium levels in the blood (hypokalemia). Loss of sodium caused by these medications increases the risk of low blood pressure.  So, it is usually recommended to take these drugs with adequate sodium chloride supplementation.

RAAS inhibitors 

Renin-angiotensin aldosterone system inhibitors (RAAS inhibitors) are recommended to treat individuals with Bartter syndrome. These inhibitors include angiotensin-converting enzyme (ACE) inhibitors, angiotensin II receptor blockers (ARBs), and aldosterone antagonists. These drugs reduce potassium and acid loss from the kidney by inhibiting the secretion of aldosterone from the adrenal glands and counteract the effects of renin on the kidneys. However, they may dangerously lower blood pressure, which is usually low in individuals with Bartter syndrome. These changes exert negative effects on kidney and cardiovascular function. Thus, these drugs should be used cautiously and carefully monitored. The drugs should be discontinued if the patient is experiencing diarrhoea and/or vomiting.

Growth hormone

In case of growth retardation and individuals having short stature, the use of growth hormone therapy is recommended.

Due to loss of fluid and electrolytes, individuals with Bartter syndrome experience salt cravings. It is encouraged to take salty foods to avoid dehydration.  A high potassium diet is recommended for affected individuals. Bartter syndrome, specifically types 4A and 4B, is associated with deafness. Cochlear implants can be used to treat deafness in these individuals. In stressful situations, electrolytes can change rapidly, requiring immediate treatment. Stress situations can include surgery, trauma, and the presence of infection.¹,⁵

Key recommendations in management

• Prenatal therapy for reducing amniotic fluid volume should be considered only after assessing to risk-to-benefit ratio
• Sodium chloride supplementation should be considered for postnatal treatment
• For potassium supplementation, potassium chloride is preferred
• Oral magnesium supplements are provided if necessary
• Nonsteroidal anti-inflammatory drugs (NSAIDs) are preferred in case of symptomatic patients. Use of gastric acid inhibitors with nonselective cyclooxygenase inhibitors should be considered
• Potassium-sparing diuretics, angiotensin-converting enzyme (ACE) inhibitors, or angiotensin receptor blockers (ARBs) are not preferred
• Use of thiazides to reduce hypercalciuria is not recommended
• Bartter syndrome becomes easier to manage and control with advancing age. The first years of life are more difficult⁶

Treatment challenges and considerations

• Side Effects and Complications
  • Medication-related issues
  • Long-term complications
• Patient Compliance
  • Importance of adherence to treatment
  • Strategies to improve compliance

Summary 

Bartter syndrome refers to a group of rare genetic disorders characterised by defects in kidney function. As a result, the kidney is unable to reabsorb salt, which is then excreted from the body. This leads to an imbalance in the fluid and electrolytes in the body. Symptoms include polyuria, polydipsia, and growth retardation. Diagnosis involves a thorough history, physical exam, and genetic testing. Management requires a multidisciplinary approach, focusing on restoring fluid and electrolyte balance with supplements and medications. NSAIDs, potassium-sparing diuretics, and RAAS inhibitors are commonly used. Proper dietary intake of salt and potassium is essential. Long-term management includes regular monitoring and addressing growth and developmental needs.

Frequently asked questions

What are the primary symptoms of bartter syndrome?

Patients often ask about the symptoms to better understand the condition and recognise potential signs in themselves or their loved ones.

How is bartter syndrome diagnosed?

People frequently inquire about the diagnostic process, including the types of tests and evaluations needed to confirm the condition.

What are the treatment options for bartter syndrome?

Patients and caregivers commonly seek information on the available treatments, including medications, dietary modifications, and other management strategies.

Can bartter syndrome be cured?

This question is crucial as it addresses the long-term outlook and whether the condition can be completely resolved or managed.

What lifestyle changes are necessary for managing bartter syndrome?

Individuals often want to know about necessary adjustments in daily routines, diet, and activities to effectively manage the condition.