What is Bartter Syndrome?
Also referred to as Bartter’s Syndrome, it is a congenital, hereditary defect within the thick ascending limb of Henle’s hoop. Its antenatal form affects the fetus during the later months of pregnancy. The condition is characterized by Hyperkalemia (low potassium levels), normal to slightly low blood pressure and alkalosis (increased blood pH).Image Source via Wikimedia Commons
It is also referred to as Salt-Wasting Nephropathy. Another condition named Gitelman syndrome is closely associated with Bartter’s Syndrome, but is considerably milder than the latter.
Bartter Syndrome Incidence
The exact prevalence of this disease is still unknown. However, the condition is estimated to affect about 1 out of every million people worldwide. According to some studies, it has a higher frequency among people living in Kuwait and Costa Rica. The disorder can occur in both children and adults, although it is more commonly seen in newborns or infants.
Bartter Syndrome Types
The classification of the condition is done by depending on the severity of the symptoms and the genetic mutation responsible for it. Its various types are:
Neonatal Type 1 Bartter’s Syndrome
This is the first type of the defect, caused by SLC12A2 (NKCC2) gene mutations.
Neonatal Type 2 Bartter’s Syndrome
It is caused by mutations in the gene controlling the instructions for ROMK/KCNJ1 protein production.
Classic or Type 3 Bartter’s Syndrome
CLCNKB gene mutations lead to the third type of the disease.
Bartter’s Syndrome along with Sensorineural Deafness
It results from mutations in the BSND gene.
Bartter’s Syndrome associated with the autosomal dominant form of Hypocalcemia
This is caused by mutations in the gene responsible for producing the CASR protein.
Bartter Syndrome Causes
The disorder is present at birth due to some inherited genetic defects that hamper the normal functioning of the body. It is mainly caused by mutations in the genes that control the instructions for producing the proteins that are responsible for transporting ions across the renal cells inside the thick ascending limb of the nephron.
There are five types of genetic mutations that cause the different forms of this syndrome.
Bartter Syndrome Pathophysiology
The genetic mutations causing the syndrome reduce the sodium absorbing ability of the kidney. As a result, patients lose excessive amounts of sodium through urine. Due to this reason, the level of aldosterone hormone increases significantly and leads the kidneys to eliminate too much potassium. This is referred to as “Potassium wasting”.
The abnormality in the functioning of kidney also causes abnormalities in the acid balance in blood, causing a condition named Hypokalemic Alkalosis, in which the patient passes excessive calcium with urine.
Bartter Syndrome Symptoms
The disorder can lead to a number of moderate to severe symptoms, including:
- Developmental delay
- Low blood pressure
- Muscle cramping
- Weakness and fatigue
- Kidney stone
- Polyuria or increased urination
- Nocturia or excessive urination at night
- Polydipsia or increased thirst
- Craving salt
- Mild dehydration
- Mental retardation
Bartter Syndrome Prevention
There is no known preventive method that can keep the disorder from occurring as it has a genetic etiology. However, it is possible to prevent the severe symptoms and complications by treating the syndrome as soon as possible.
Bartter Syndrome Diagnosis
Doctors suspect the presence of Bartter’s Syndrome if a patient has low potassium levels in the blood. It is generally lower than 2.5 mEq/L. However, unlike other kidney disorders that cause high blood pressure, this condition tends to result in low blood pressure. Other diagnostic criteria include:
- High potassium levels in the urine
- Low blood chloride levels
- High amounts of chloride in urine
- High levels of aldosterone and renin hormone in the blood
Blood tests and urine tests are mainly used for making the diagnosis. Urine tests are very useful for ruling out other causes, like using too much laxatives and diuretics, which may lead to similar symptoms. Kidney biopsy is another useful diagnostic test that helps to determine whether the patient has Juxtaglomerular apparatus, a disorder characterized by extreme growth of the kidney cells. However, this symptom is usually not present in affected children.
Bartter Syndrome Differential Diagnosis
It is important to rule out the following conditions while diagnosing this syndrome:
- Gitelman syndrome
- Diuretic abuse
- Hyperprostaglandin E syndrome
- Activating mutations of CaSR calcium-sensing receptor
- Familial hypomagnesemia with hypercalciuria or nephrocalcinosis
- Cyclical vomiting
- Gullner syndrome (Familial hypokalemic alkalosis along with proximal tubulopathy)
- Mineralocorticoid excess
- Cystic fibrosis
- Pyloric stenosis
- Congenital chloride diarrhea
- Hypochloremic alkalosis
Bartter Syndrome Treatment
At present, there is no specific treatment that can cure the disorder. Following a proper diet is recommended for the patients to get the essential nutrition for keeping its progression under control. They have to follow a diet containing plenty of potassium-rich food and take potassium supplements as it is very important to maintain the potassium level in the blood above 3.5 mEq/L for managing the disease. Many affected individuals need to consume ample amounts of salt and take magnesium supplements as well. Medicines that can prevent the kidney from eliminating potassium from the body may also be necessary. In some cases, a doctor may prescribe high doses of NSAIDs (nonsteroidal anti-inflammatory drugs) to stop the loss of vitamins and minerals.
Children suffering from growth retardation due to this syndrome can be treated with growth hormones. Sometimes, prostaglandin inhibitors are required for lowering the abnormally high prostaglandin levels.
Bartter Syndrome Prognosis
The outcome varies on the basis of the age of patients and the duration of the condition. The long-term prognosis is not certain in most cases. Infants with serious growth problems generally grow normally with early treatment. Proper management allows affected individuals to have a long life expectancy and lead a normal healthy life, but they usually have to remain under treatment for the rest of their lives.
Bartter Syndrome Complications
Many patients do not develop any serious complications of the disease. However, Bartter’s Syndrome may lead to some serious complications like gout and complete renal failure.
Bartter Syndrome Support Groups
There are numerous forums and support groups that help the patients to cope with this disorder. These organizations include:
American Kidney Fund, Inc.
6110 Executive Boulevard
Suite – 1010
Rockville, Maryland 20852
March of Dimes Birth Defects Foundation
1275 Mamaroneck Avenue
White Plains, New York 10605
National Kidney Foundation
30 East 33rd Street
New York, NY 10016
Bartter Syndrome is a potentially dangerous genetic condition that requires early diagnosis along with proper treatment so that the patients can live as normally as possible. Infants with the disease can have normal growth and can participate in the usual activities with ongoing treatment.