Warning Signs Of Bartter Syndrome

August 1, 2023

Bartter syndrome is a group of disorders characterized by genetically precipitated kidney function defects. The defects in Bartter syndrome make the kidney unable to effectively reabsorb salt from the blood, causing numerous electrolyte imbalances in the affected individual's body. Calcium, sodium, potassium, magnesium, and chloride are the mineral salts most commonly affected in individuals with Bartter syndrome. Mutations in one of several different genes can cause an individual to have Bartter syndrome, including the SLC12A1, KCNJ1, CLCNKB, BSND, CLCNKA, CLCNKB, and MAGED2 genes.

Diagnosis of Bartter syndrome is made with the use of a thorough clinical evaluation, blood tests, urine analysis, and molecular genetic testing. Each patient is treated differently according to their specific symptoms. Symptoms of Bartter syndrome range widely from one affected individual to the next and may have an onset anywhere from before birth through mid-adulthood.

Slower Growth And Development

Individuals who have Bartter syndrome can exhibit slower growth and development. Many subtypes of Bartter syndrome develop before the affected individual's birth. In the antenatal Bartter syndromes, abnormal functioning of the kidneys while in utero can cause excessive production of urine, leading to an accumulation of amniotic fluid around the unborn child that can cause complications like pre-term birth. Prematurity causes infants to experience a slower rate of cognitive and motor development. Issues linked to Bartter syndrome, such as frequent dehydration, vomiting, and constipation, can contribute to slower growth and development because they cause a decrease in appetite and weight loss.

Children affected by Bartter syndrome often do not reach developmental milestones as quickly as peers of the same age do. Many infants diagnosed with Bartter syndrome experience failure to thrive or fail to gain weight as expected. Delays in growth and development tend to worsen progressively as patients progress into adulthood. In affected individuals, Bartter syndrome has been implicated in the cause of adulthood short stature.

Constipation

Individuals affected by Bartter syndrome can experience constipation. When an individual is constipated, their stool is usually dry and hard, painful to pass, and may cause tissue injury. Bartter syndrome patients have a defect in the tubes of the kidneys causes too much salt excretion and subsequent fluid loss. Fluid volume depletion in the blood triggers the Renin-angiotensin-aldosterone system. Increased aldosterone levels cause hydrogen ion accumulation that results in the depletion of potassium. Low blood potassium draws more potassium out of the intestinal muscle cells into the blood. Low potassium in the intestinal muscle cells causes them to have more resistance to membranous electrical current passage.

A reduction in muscle cell contraction in the intestinal tissues results from the decreased passage of electrical currents. An individual's stool stagnates when it does not have enough contraction to move it through the gastrointestinal tract. Stagnation in the large intestine causes the colon to absorb too much fluid from the stool inappropriately. When the stool passes infrequently, is dry, and is hard, the individual experiences constipation.

Cravings For Salt

Cravings for salt are common in Bartter syndrome patients due to the adverse effects of their disorder. The tubules in the kidneys are responsible for filtering the blood of waste substances and salt to maintain homeostasis in the body. When blood volume is too low, salt is reabsorbed into the blood from the kidneys. When the blood volume is too high, the kidneys remove sodium from the blood for excretion through the urine. Individuals who have Bartter syndrome have a mutation in the gene that encodes how the kidney tubules should function.

The specific channel dysfunction varies between subtypes of Bartter syndrome, but they all cause a disturbance in the salt reabsorption process. This malfunction results in too much salt being removed from the body through the urine. The mechanism the body uses to maintain a healthy blood pressure relies on the ability of the kidneys to absorb and reabsorb salt. This mechanism becomes impaired in Bartter syndrome, prompting the body to seek sources of sodium and fluids elsewhere. One method is increasing the individual's cravings for salt. Increased salt intake allows for better fluid retention, which helps replace the excessive quantity of salt and fluids being removed through the urine.

Severe Thirst

Severe thirst is a prevalent symptom in individuals with Bartter syndrome. The underlying abnormalities in the kidneys of individuals affected by Bartter syndrome cause the loss of chloride, potassium, and sodium through the urine. The fluid balance in the body relies on sodium. The body requires a perfect ratio of fluid and sodium. If sodium concentration is greater in one tissue than another, water is pulled from lower sodium tissues to the high sodium tissue, and if this concentration is lower in one tissue than another, water is forced away from the low sodium tissue to tissue with more sodium.

Fluids follow sodium when referring to the human body. This mechanism is helpful in individuals with kidneys that allow for sodium movement to and from the blood. However, kidneys affected by Bartter syndrome cannot reabsorb salt into the blood when it is needed. This malfunction means the concentration of salt in urine is always greater, so fluid is constantly pulled from the blood to the urine to correct the imbalance. This dysfunctional process causes dehydration, which tells the brain to induce severe thirst.

Frequent Urination

Bartter syndrome patients also commonly deal with a frequent need to urinate. The average healthy individual urinates six or seven times within twenty-four hours while drinking two liters of fluids. At the same fluid consumption rate, urinating more than seven times within twenty-four hours is considered frequent urination. Frequent urination can occur for numerous reasons related to bladder malfunction or excessive urine production. Bartter syndrome is defined by a dysfunction of the kidney, causing excessive amounts of salt to be wasted through urine. This wasting of salt should only occur when the kidneys are prompted, like in hypertensive conditions.

The reason being that removal of sodium from the blood forces the removal of fluid from the blood, and both are excreted through urine. However, the kidneys affected by Bartter syndrome are unable to reverse the movement of sodium out of the body, causing the production of excessive amounts of urine. The bladder fills up much quicker, prompting the patient to empty it at a greater frequency than that of an unaffected individual.

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