What is bartter syndrome?
Bartter syndrome is an over-all term for a group of rare genetic disorders in which there are specific flaws in kidney function. These defects damage the kidney’s ability to reabsorb salt and cause imbalances in the various electrolytes and fluid attentions in the body. The electrolytes affected are primarily mineral salts such as potassium, calcium, magnesium, sodium, and chloride.
The symptoms and severity of Bartter syndrome vary from one individual to another and can range from mild to severe. The age of onset of overt symptoms can variety from before birth to adulthood. Bartter syndrome is caused by alterations (changes) in one of several different genes. Treatment is aimed at correcting the electrolyte imbalances through the use of supplements and certain medications such as nonsteroidal anti-inflammatories (NSAIDs) and diuretics.
Causes of bartter syndrome
Bartter syndrome can be caused by mutations in any of several genes; the genetic cause in each case corresponds to the type of Bartter syndrome that each affected individual has. Type I is due to mutations in the SLC12A1 gene. Type II is caused by mutations in the KCNJ1 genetic factor. Type III results from mutations in the CLCNKB genetic factor.
Type IV can be caused by mutations in the BSND gene or by a combination of mutations in the CLCNKA and CLCNKB genes. The last variant, type V, has associated mutations in the CASR gene. In some people with Bartter syndrome, the genetic cause of the disorder is unknown; There may be other genes that cause the condition that has not yet been identified.
All of these genes are essential for normal kidney function – they are involved in the kidneys’ ability to reabsorb salt. Abnormal variations in these genes affect these abilities, allowing the loss of excess salt through the urine and also affecting the reabsorption of other things, such as potassium and calcium. The resulting imbalance of these in the body leads to the signs and symptoms of Bartter syndrome.
Symptoms of bartter syndrome
This disease usually occurs in childhood. Symptoms include:
- The rate of weight gain is much lower than that of other children of similar age and sex (stunting)
- Need to urinate more repeatedly than usual (urinary frequency)
- Low blood pressure
- Kidney stones
- Muscle cramps and weakness
Diagnosis of bartter syndrome
- Electrolyte levels in serum and urine
- Exclusion of similar disorders
Bartter syndrome and Gitelman syndrome should be supposed in children with characteristic symptoms or related laboratory abnormalities, such as metabolic alkalosis and hypokalemia. Measurement of urinary electrolytes shows elevated levels of sodium, potassium, and chloride that are inappropriate for the euvolemic or hypovolemic state of the patient. Diagnosis is made by excluding other disorders:
- Primary and secondary aldosteronism can often be distinguished by the presence of hypertension and normal or low plasma renin levels (see Differential Diagnosis of Aldosteronism).
- Surreptitious vomiting or laxative exploitation can often be distinguished by low levels of urinary chloride (usually <20 mmol / L).
- Surreptitious diuretic abuse can often be distinguished by low urinary chloride levels and a urine diuretic test.
A 24-hour measurement of urine calcium or urine calcium/creatinine ratio can help distinguish the two syndromes; levels are typically normal too high in Bartter syndrome and low in Gitelman syndrome.
Complete Metabolic Panel (CMP) icon
Definitive diagnosis, including identification of disease subtypes, is made using genetic tests, which are now increasingly available.
Treatment of bartter syndrome
It is treated by eating foods rich in potassium or taking potassium supplements.
Many people also need salt and magnesium supplements. Medications that block the kidney’s ability to remove potassium may be needed. High doses of non-steroidal anti-inflammatory drugs (NSAIDs) can also be used.
- Potassium wasting
- Salt-wasting nephropathy
The risk factors for this disease remain unknown because the disease has its origin in genetic mutations of unknown causes.
There are no known prevention methodologies for this disease because the disease results from mutations of the genes.