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Bartter's Syndrome

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Synonyms of Bartter's Syndrome

Disorder Subdivisions

General Discussion

Bartter's syndrome (BS) is a group of conditions involving enlargement of certain kidney cells, blood that is more alkaline than normal, high levels of potassium and chloride in the urine, loss of potassium from the kidneys (renal potassium wasting), dehydration, muscle weakness, muscle cramps, frequent urination, and growth deficiency, potentially resulting in dwarfism. It is thought to be caused by a defect in the body's ability to reabsorb potassium. Individuals with Bartter syndrome have a disturbed acid-base ratio (i.e., an accumulation of base or loss of acid) associated with a loss of potassium (hypokalemic alkalosis). Low amounts of potassium may result from overproduction of a certain hormone (aldosterone) that is essential in controlling blood pressure and regulating sodium and potassium levels (hyperaldosteronism). Even so, the blood pressure of people with Bartter syndrome is normal.

Symptoms

Symptoms and their intensity vary among the various types of Bartter's syndrome. In general, the syndrome is characterized by growth deficiency, potentially resulting in short stature; muscle weakness, cramps, and/or loss of potassium from the kidneys (renal potassium wasting).

Loss of potassium may result from overproduction of a certain hormone (aldosterone) that is essential in controlling blood pressure and regulating sodium and potassium levels (hyperaldosteronism). Low potassium levels may be associated with a disturbance in an affected individual's acid-base ratio (i.e., an accumulation of base or loss of acid). This is known as hypokalemic alkalosis.

Specific signs and symptoms associated with Bartter's syndrome include normal blood pressure, low blood chloride; blood that is more alkaline than normal, high blood levels of the hormones rennin and aldosterone, both of which are involved in the regulation of potassium by the kidney; and high levels of potassium and chloride in the urine.

Of the various types of this syndrome, the one known as Gitelman syndrome appears generally to be the mildest and to present later in life, often in adults without symptoms (asymptomatic) who are found to have lack or loss of potassium (hypokalemia) on routine laboratory testing.

The type called classic Bartter's syndrome usually presents in infants. Symptoms of the classic type may include salt craving, fatigue, muscle weakness, growth retardation and developmental delay.

The type known as antenatal Bartter's syndrome is the most severe and may become life-threatening. In the newborn, it may present with fever, vomiting, diarrhea, failure to thrive, growth retardation, facial anomalies such as a triangular face, prominent forehead, large eyes, protruding ears, and drooping mouth, severe electrolyte imbalance; and high potassium and chloride excretion in the urine.

Causes

Bartter's syndrome is thought to be caused by a defect in the body's ability to reabsorb potassium. As a result, an excessive amount of potassium is excreted from the body. This is known as potassium wasting.

Bartter's syndrome is usually hereditary and the pattern of inheritance is autosomal recessive. In recent years, researchers have worked to identify the genes associated with the various forms of this syndrome, including subgroups within the antenatal group.

Chromosomes, which are present in the nucleus of human cells, carry the genetic information for each individual. Human body cells normally have 46 chromosomes. Pairs of human chromosomes are numbered from 1 through 22 and the sex chromosomes are designated X and Y. Males have one X and one Y chromosome and females have two X chromosomes. Each chromosome has a short arm designated "p" and a long arm designated "q". Chromosomes are further sub-divided into many bands that are numbered.

Genetic diseases are determined by the combination of genes for a particular trait that are on the chromosomes received from the father and the mother.

Recessive genetic disorders occur when an individual inherits the same abnormal gene for the same trait from each parent. If an individual receives one normal gene and one gene for the disease, the person will be a carrier for the disease, but usually will not show symptoms. The risk for two carrier parents to both pass the defective gene and, therefore, have an affected child is 25% with each pregnancy. The risk to have a child who is a carrier like the parents is 50% with each pregnancy. The chance for a child to receive normal genes from both parents and be genetically normal for that particular trait is 25%. The risk is the same for males and females.

All individuals carry a few abnormal genes. Parents who are close relatives (consanguineous) have a higher chance than unrelated parents to both carry the same abnormal gene, which increases the risk to have children with a recessive genetic disorder.

Affected Populations

Bartter's syndrome affects children much more frequently than adults, but it has been reported to occur at all ages. Males and females are affected in equal numbers. The neonatal form of the disorder may be suspected before birth and may be diagnosed in the youngest of newborns. There is no racial, ethnic, or gender predilection.

Related Disorders

Symptoms of the following disorders can be similar to those of Bartter's syndrome. Comparisons may be useful for a differential diagnosis:

Hypokalemia
Hypokalemia refers to a low level of potassium in the blood. Potassium is an electrolyte (charged particle) that is important to the function of the nerve and muscle cells, including the heart. Hypokalemia is most common in people with diseases that affect kidney function, people who take diuretics, and people with eating disorders.

Most of the body's potassium is stored inside various cells and organs, with only a small amount found in the blood. The body maintains a balance of potassium in the blood by matching the amount of potassium taken in with the amount excreted (put out) by the kidneys.

Hypokalemia occurs when the body releases too much potassium, such as through severe vomiting, diarrhea, or sweating during intense exercise. It may also be a consequence of diseases that affect kidney function so that the kidneys may excrete too much potassium, or may not be able to match their output to the body's potassium intake. Diseases that can cause hypokalemia include Liddle syndrome, Cushing's syndrome, Fanconi syndrome, and Bartter syndrome.

Certain drugs called diuretics increase the body's urine output, which can also cause hypokalemia. Hypokalemia can be caused by overuse of laxatives; by eating disorders such as bulimia, which involves self-induced vomiting; and by prolonged fasting and starvation. Although it is less likely, hypokalemia can also be caused by not eating enough foods that contain potassium.

Renal tubular acidosis
Renal tubular acidosis (RTA) is characterized by the impaired ability of the kidney to secrete hydrogen or to reabsorb bicarbonate which can lead to chronic high levels of acid in the blood and urine (metabolic acidosis) accompanied by potassium depletion.

Standard Therapies

Diagnosis
The diagnosis of Bartter syndrome is usually made on the basis of the results of blood tests. If Bartter syndrome is suspected, the potassium level in the blood will be tested. The combination of low blood potassium concentrations with normal blood pressure is a possible indicator of this disorder. Blood tests will also confirm low blood chloride, and that the blood acid/base balance is skewed towards the base, or that the blood is more alkaline than usual.

Tests to determine the concentration of the hormones renin and aldosterone may also be ordered. High blood levels of these hormones would support the diagnosis of Bartter syndrome.

Further confirmation comes from the high levels of potassium and chloride in the urine. Such signs suggest that the ability of the kidney to control the concentration of these electrolytes is failing or has been lost. These same signs and symptoms can also occur in people who have taken excessive amounts of diuretics or laxatives. Urine tests can be done to exclude these causes.

Treatment
Treatment of Bartter syndrome depends on the type of the syndrome that is present but focuses primarily on preventing the loss of excessive amounts of potassium. This may include medications, supplements, and a diet rich in potassium. Genetic counseling may be of benefit for patients and their families.

Investigational Therapies

Information on current clinical trials is posted on the Internet at www.clinicaltrials.gov. All studies receiving U.S. government funding, and some supported by private industry, are posted on this government web site.

For information about clinical trials being conducted at the NIH Clinical Center in Bethesda, MD, contact the NIH Patient Recruitment Office:
Tollfree: (800) 411-1222
TTY: (866) 411-1010
Email: prpl@cc.nih.gov

For information about clinical trials sponsored by private sources, contact:
www.centerwatch.com

Organizations related to Bartter's Syndrome

References

TEXTBOOKS
Hodgson DM, Zingman LV, Terzic A. Bartter Syndrome. In: NORD Guide to Rare Disorders. Lippincott Williams & Wilkins. Philadelphia, PA. 2003:309-11.

Kasper, DL, Fauci AS, Longo DL, et al., eds. Harrison's Principles of Internal Medicine. 16th ed. McGraw-Hill Companies. New York, NY; 2005:1697-98.

Larsen PR, Kronenberg HM, Melmed S, Polonsky KS, eds. Williams Textbook of Endocrinology. 10th ed. Elsevier Saunders. Philadelphia, PA. 2003:578-79.

Scriver CR, Beaudet AL, Sly WS, et al., eds. The Metabolic Molecular Basis of Inherited Disease. 8th ed. McGraw-Hill Companies. New York, NY; 2001:5409-11.

REVIEW ARTICLES
Calo LA. Vascular tone control in humans: insights from studies in Bartter's/Gitelman's syndromes. Kidney Int. 2006;69:963-66.

Landau D. Potassium handling in health and disease: lessons from inherited tubulopathies. Pediatr Endocrinol Rev. 2004;2:203-08.

Reinalter SC, Jeck N, Peters M, Seyberth HW. Pharmacotyping of hypokalaemic salt-losing tubular disorders. Acta Physiol Scand. 2004;181:513-21.

Naesens M, Steels P, Verberckmoes R, Vanrenterghem Y, Kuypers D. Barter's and Gitelman's syndromes: from gene to clinic. Nephron Physiol. 2004;106:p65-78.

FROM THE INTERNET
McKusick VA, ed. Online Mendelian Inheritance In Man (OMIM). The Johns Hopkins University. Bartter Syndrome, Antenatal, Type 1. Entry Number; 60178: Last Edit Date; 5/26/2005.

McKusick VA, ed. Online Mendelian Inheritance In Man (OMIM). The Johns Hopkins University. Bartter Syndrome, Antenatal, Type 2. Entry Number; 241200: Last Edit Date; 6/3/2005.

McKusick VA, ed. Online Mendelian Inheritance In Man (OMIM). The Johns Hopkins University. Bartter Syndrome, Type 3. Entry Number; 607364: Last Edit Date; 11/17/2005.

McKusick VA, ed. Online Mendelian Inheritance In Man (OMIM). The Johns Hopkins University. Bartter Syndrome, Infantile, with Sensorineural Deafness. Entry Number; 602522: Last Edit Date;.

McKusick VA, ed. Online Mendelian Inheritance In Man (OMIM). The Johns Hopkins University. Calcium-Sensing Receptor; CASR. Entry Number; 601199: Last Edit Date; 12/20/2005.

Bartter's syndrome. Medical Encyclopedia. MedlinePlus. Update Date: 11/10/2004. 3pp.
www.nlm.nih.gov/medlineplus/ency/article/000308.htm

Colusi G. Bartter syndrome. Orphanet encyclopedia. March 2005. 6pp.
www.orpha.net/data/patho/GB/uk-Bartter.pdf

Devarajan P, Imam A. Bartter Syndrome. emedicine. Last Updated: February 9, 2006. 8pp.
www.emedicine.com/ped/topic210.htm

Report last updated: 2007/09/23 00:00:00 GMT+0