Bartter syndrome is a group of rare genetic condition that affects the kidneys. This occurs when the kidneys are unable to reabsorb salt causing an imbalance in the electrolyte and fluid of the body. The electrolytes are the mineral salts consisting of potassium, calcium, magnesium, sodium and chloride. This syndrome is presented in the beginning of infancy affecting the child’s ability to gain weight and grow at the expected rate. This condition can also be detected before the birth with the presence of fluid build-up around the fetus in a condition known as polyhydramnios which can induce premature birth. The two types of bartter syndrome consist of the one that begins before the birth (antenatal) and the other affects the early childhood (classical form). Further, bartter syndrome is distinguished by the different genetic mutation responsible for the different types of this condition. The exact prevalence of this barter syndrome is not known but is estimated to affect 1 in a million individuals globally.
Causes
Bartter syndrome is inherited in an autosomal recessive manner meaning both the copies of the gene in each cell, one from each parent, contain the mutated gene. There are five different genetic mutations associated with the different forms of bartter syndrome. The type 1 is responsible for the genetic mutation in the gene SLC12A1, type 2 in the gene KCNJ1 and mutation in the gene CLCNKB causes type 3. The genetic mutation in the gene BSND is responsible for the onset of type 4 or a combination of CLCNKA and CLCNKB. These 5 different genes are responsible for the production of certain proteins necessary for the re-absorption of salt by the kidneys and the genetic defect causes excess salt to be lost in the urine. In some cases, the genetic cause of this syndrome remains unknown.
Symptoms
Initial symptoms may begin in the infancy with problems in gaining weight and growing at the expected rate. The loss of excessive salt in the urine causes dehydration, constipation and increase in the urine volume. The excess amount of calcium lost in their urine can cause osteopenia (weak bones) and the calcium deposit in the kidney creates nephrocalcinosis (hardening of the kidney tissue). In addition, the low concentration of potassium results in fatigue, muscle weakness and cramping. These individuals have the need to urinate more often than normal, prone to develop kidney stones and have low blood pressure.
Diagnosis
A diagnosis of bartter syndrome consists of a thorough evaluation of the patient’s history and identifying the features associated with this condition. These individuals usually have elevated levels of electrolytes in the blood and urine, which can be confirmed with the high levels of renin and aldosterone in the blood. The other diagnostic tests include detecting the elevated levels of sodium, potassium, calcium, chloride in the urine and low blood chloride. The molecular genetic testing can identify the mutated gene and confirm the diagnosis.
Treatment
There is no cure for bartter syndrome and the affected individual usually requires lifelong medications and supplements. The treatment is based on correcting the abnormalities associated with the electrolytes by replacing the lost materials such as magnesium and potassium in the form of supplements. Certain medications can help with retaining the potassium in the body and preventing its loss in the urine. Increased fluid intake is necessary along with a diet rich in potassium. Children with short stature may be administered growth hormones to treat the growth retardation.
References
https://rarediseases.org/rare-diseases/bartters-syndrome/
https://ghr.nlm.nih.gov/condition/bartter-syndrome#inheritance
https://medlineplus.gov/ency/article/000308.htm