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Bartter Syndrome and Gitelman Syndrome
In Bartter syndrome and Gitelman syndrome, a defect of the kidney tubules causes the kidneys to excrete excessive amounts of electrolytes (potassium, sodium, and chloride), resulting in growth, electrolyte, and sometimes nerve and muscle abnormalities.
Bartter syndrome and Gitelman syndrome are hereditary and are usually caused by a recessive gene. Thus, a person with Bartter syndrome or Gitelman syndrome has usually inherited two recessive genes for the disorder, one from each parent. Because two genes are needed when a recessive gene is involved, there are usually no other immediate family members with the syndrome. Although both are rare, Gitelman syndrome is more common than Bartter syndrome.
In Bartter syndrome and Gitelman syndrome, the kidneys cannot reabsorb salt (sodium chloride) normally from the kidney tubule. Thus, the kidneys excrete excessive amounts of sodium and chloride in the urine. The loss of sodium and chloride leads to excessive urine production and thus mild dehydration. Mild dehydration causes the body to produce more of the enzyme renin and the hormone aldosterone, which help regulate blood pressure. The increase in aldosterone increases potassium and acid secretion in the kidneys, leading to low blood potassium (hypokalemia) and loss of acids in the blood that causes blood pH to be alkaline (a disorder called metabolic alkalosis—see Alkalosis). Although the tubules are affected in both syndromes, the kidneys are otherwise unaffected and filter out waste products normally.
The main differences between the two syndromes are the genes that are involved, the part of the tubule that is affected, and the age at which symptoms begin.
Symptoms of Bartter syndrome may appear before birth or during infancy or early childhood. Symptoms of Gitelman syndrome may appear from late childhood to adulthood. Children with these syndromes have symptoms that are similar to those of people who take drugs called diuretics, which increase urine output and can cause chemical imbalances in the blood. However, unlike with taking a drug, in Bartter syndrome or Gitelman syndrome, symptoms cannot be ended by stopping a drug.
Fetuses with Bartter syndrome may grow poorly while in the womb. Some children are born prematurely and may be intellectually disabled. Children with Bartter syndrome and sometimes those with Gitelman syndrome may have poor growth and developmental delays. The loss of magnesium, calcium, or potassium can lead to muscle weakness, cramping, spasms, or fatigue, particularly in people with Gitelman syndrome. Children may have excessive thirst, may produce large amounts of urine, and may have nausea and vomiting. The loss of sodium and chloride leads to chronic mild dehydration. Abnormally low blood pressure (hypotension) may occur. In addition, people with Bartter syndrome may develop kidney stones or a build up of calcium in the kidneys (called nephrocalcinosis) because they have large amounts of calcium in their urine. However, people with Gitelman syndrome do not develop these problems.
Doctors suspect Bartter syndrome or Gitelman syndrome in children who have characteristic symptoms or who have abnormal levels of electrolytes in their blood and urine that are found when laboratory tests are done for other reasons. The diagnosis is confirmed by finding high levels of renin and aldosterone in the blood and high levels of sodium, chloride, and potassium in the urine. Genetic testing is available but usually is not done.
Because the defective functions of the tubule cells in the kidneys cannot be corrected, treatment is lifelong and is aimed at correcting the hormonal, fluid, and electrolyte abnormalities. People take supplements containing the substances that are lost in the urine, such as potassium and magnesium, and also increase their fluid intake.
Certain drugs can be helpful. People with Bartter syndrome are given nonsteroidal anti-inflammatory drugs (NSAIDs), such as indomethacin, and a drug that reduces excretion of potassium into the urine, such as spironolactone (which also blocks the action of aldosterone) or amiloride. Spironolactone or amiloride is also given to people with Gitelman syndrome. NSAIDs are not helpful in Gitelman syndrome. For both syndromes, doctors may give angiotensin-converting enzyme (ACE) inhibitors, which block the increased production of aldosterone. Doctors may give growth hormone to children who are very short.
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