Bartter Syndrome: A Systematic Review of Case Reports and Case Series

Background and Objectives: Bartter syndrome (BS) is a rare group of autosomal-recessive disorders that usually presents with hypokalemic metabolic alkalosis, occasionally with hyponatremia and hypochloremia. The clinical presentation of BS is heterogeneous, with a wide variety of genetic variants. The aim of this systematic review was to examine the available literature and provide an overview of the case reports and case series on BS. Materials and Methods: Case reports/series published from April 2012 to April 2022 were searched through Pubmed, JSTOR, Cochrane, ScienceDirect, and DOAJ. Subsequently, the information was extracted in order to characterize the clinical presentation, laboratory results, treatment options, and follow-up of the patients with BS. Results: Overall, 118 patients, 48 case reports, and 9 case series (n = 70) were identified. Out of these, the majority of patients were male (n = 68). A total of 21 patients were born from consanguineous marriages. Most cases were reported from Asia (73.72%) and Europe (15.25%). In total, 100 BS patients displayed the genetic variants, with most of these being reported as Type III (n = 59), followed by Type II (n = 19), Type I (n = 14), Type IV (n = 7), and only 1 as Type V. The most common symptoms included polyuria, polydipsia, vomiting, and dehydration. Some of the commonly used treatments were indomethacin, potassium chloride supplements, and spironolactone. The length of the follow-up time varied from 1 month to 14 years. Conclusions: Our systematic review was able to summarize the clinical characteristics, presentation, and treatment plans of BS patients. The findings from this review can be effectively applied in the diagnosis and patient management of individuals with BS, rendering it a valuable resource for nephrologists in their routine clinical practice.

Genetic diagnosis and treatment of hereditary renal tubular disease with hypokalemia and alkalosis

Renal tubules play an important role in maintaining water, electrolyte, and acid-base balance. Renal tubule dysfunction can cause electrolyte disorders and acid-base imbalance. Clinically, hypokalemic renal tubular disease is the most common tubule disorder. With the development of molecular genetics and gene sequencing technology, hereditary renal tubular diseases have attracted attention, and an increasing number of pathogenic genes related to renal tubular diseases have been discovered and reported. Inherited renal tubular diseases mainly occur due to mutations in genes encoding various specific transporters or ion channels expressed on the tubular epithelial membrane, leading to dysfunctional renal tubular reabsorption, secretion, and excretion. An in-depth understanding of the molecular genetic basis of hereditary renal tubular disease will help to understand the physiological function of renal tubules, the mechanism by which the kidney maintains water, electrolyte, and acid-base balance, and the relationship between the kidney and other systems in the body. Meanwhile, understanding these diseases also improves our understanding of the pathogenesis of hypokalemia, alkalosis and other related diseases and ultimately promotes accurate diagnostics and effective disease treatment. The present review summarizes the most common hereditary renal tubular diseases (Bartter syndrome, Gitelman syndrome, EAST syndrome and Liddle syndrome) characterized by hypokalemia and alkalosis. Further detailed explanations are provided for pathogenic genes and functional proteins, clinical manifestations, intrinsic relationship between genotype and clinical phenotype, diagnostic clues, differential diagnosis, and treatment strategies for these diseases.

Clinical Course of Patients with Bartter Syndrome

INTRODUCTION

Bartter syndrome (BS) is a salt losing tubulopathy due to impairment of the transport mechanisms at the thick ascending limb of the Henle's loop. The aim of this study was to report the clinical course of patients with BS.

METHODS

Patients with BS were followed from 1996 to 2020 and enrolled to a systematic protocol to confirm primary BS by evaluating the metabolic derangements, nephrolithiasis and nephrocalcinosis. Treatment was based on standard guidelines. Comparisons were made between data at baseline and at the last visit.

RESULTS

A total of 13 patients (7 males) with primary BS were analyzed. Two patients had a mutation of the KCNJ1 gene. Age at diagnosis was 3 ± 4.5 years and the follow-up period was 11.19 ± 6.76 years. Metabolic alkalosis was initially detected in 76.92% and remained stable at the last visit (P > .05). Hypokalemia was present in 61.5% of patients at diagnosis, but sustained in 38.46% at the last visit (P < .05). Urine calcium level was 13.3 ± 9.6 mg/ kg/d at the first visit, and significantly reduced to 3.7 ± 2.0 mg/ kg/d at the last visit (P < .05). Nephrocalcinosis was detected by first kidney ultrasonography in 53.8% of patients. Kidney function was preserved, with a glomerular filtration rate of 120.1 ± 28.7 mL/min/ 1.73m2 at last visit. Growth was completely recovered in 71.42% and partially improved in 14.28% of patients after treatment, respectively. All patients received indomethacin and potassium chloride salts.

CONCLUSIONS

Long-term follow-up of this cohort of BS showed favorable outcomes after treatment resulting in metabolic normalization and growth catch-up in most patients.  DOI: 10.52547/ijkd.6657.

Bartter and Gitelman syndromes

Bartter and Gitelman syndromes belong to salt-losing tubulopathies. These rare diseases may be associated with severe electrolyte disorders. Early identification of tubulopathies is essential for appropriate management. Progress in molecular genetics enabled the identification of genes and pathophysiologic mechanisms associated with these diseases. Here, we review etiology and diagnostics of these disorders from the light of current knowledge. Additionally, we discuss contemporary therapeutic approaches.

Molecular Basis, Diagnostic Challenges and Therapeutic Approaches of Bartter and Gitelman Syndromes: A Primer for Clinicians

Gitelman and Bartter syndromes are rare inherited diseases that belong to the category of renal tubulopathies. The genes associated with these pathologies encode electrolyte transport proteins located in the nephron, particularly in the Distal Convoluted Tubule and Ascending Loop of Henle. Therefore, both syndromes are characterized by alterations in the secretion and reabsorption processes that occur in these regions. Patients suffer from deficiencies in the concentration of electrolytes in the blood and urine, which leads to different systemic consequences related to these salt-wasting processes. The main clinical features of both syndromes are hypokalemia, hypochloremia, metabolic alkalosis, hyperreninemia and hyperaldosteronism. Despite having a different molecular etiology, Gitelman and Bartter syndromes share a relevant number of clinical symptoms, and they have similar therapeutic approaches. The main basis of their treatment consists of electrolytes supplements accompanied by dietary changes. Specifically for Bartter syndrome, the use of non-steroidal anti-inflammatory drugs is also strongly supported. This review aims to address the latest diagnostic challenges and therapeutic approaches, as well as relevant recent research on the biology of the proteins involved in disease. Finally, we highlight several objectives to continue advancing in the characterization of both etiologies.

Diagnosis and management of Bartter syndrome: executive summary of the consensus and recommendations from the European Rare Kidney Disease Reference Network Working Group for Tubular Disorders

Bartter syndrome is a rare inherited salt-losing renal tubular disorder characterized by secondary hyperaldosteronism with hypokalemic and hypochloremic metabolic alkalosis and low to normal blood pressure. The primary pathogenic mechanism is defective salt reabsorption predominantly in the thick ascending limb of the loop of Henle. There is significant variability in the clinical expression of the disease, which is genetically heterogenous with 5 different genes described to date. Despite considerable phenotypic overlap, correlations of specific clinical characteristics with the underlying molecular defects have been demonstrated, generating gene-specific phenotypes. As with many other rare disease conditions, there is a paucity of clinical studies that could guide diagnosis and therapeutic interventions. In this expert consensus document, the authors have summarized the currently available knowledge and propose clinical indicators to assess and improve quality of care.

Bartter Syndrome and Gitelman Syndrome

Bartter and Gitelman syndromes are conditions characterized by renal salt-wasting. Clinical presentations range from severe antenatal disease to asymptomatic with incidental diagnosis. Hypokalemic hypochloremic metabolic alkalosis is the common feature. Bartter variants may be associated with polyuria and weakness. Gitelman syndrome is often subtle, and typically diagnosed later life with incidental hypokalemia and hypomagnesemia. Treatment may involve fluid and electrolyte replenishment, prostaglandin inhibition, and renin-angiotensin-aldosterone system axis disruption. Investigators have identified causative mutations but genotypic-phenotypic correlations are still being characterized. Collaborative registries will allow improved classification schema and development of effective treatments.

[Poor weight gain, recurrent metabolic alkalosis and hypokalemia in a neonate]

The study reports a female neonate with a gestational age of 29⁺² weeks and a birth weight of 1 210 g. Ten minutes after birth, the neonate was admitted to the hospital due to shortness of breath. Several days after birth, the neonate presented with hyperglycemia, polyuria, and poor weight gain, accompanied by azotemia, hypochloremic metabolic alkalosis, hypokalemia, and hyponatremia. Laboratory examinations showed elevated levels of aldosterone, renin, and angiotensin II. Gene detection revealed SLC12A1 gene mutation. Neonatal Bartter syndrome was thus confirmed. The neonate was treated with sodium and potassium supplements, and was followed up for 8 months. During the follow-up, the mental and neural development of the neonate was almost normal at the corrected age, and regular reexaminations showed slight metabolic alkalosis and almost normal electrolyte levels. For the neonates who have the symptoms of unexplainable polyurine and electrolyte disorders, it is important to examine the levels of aldosterone, renin and angiotensin. A definite diagnosis of neonatal Bartter syndrome can be made based on the presence of SLC12A1 gene mutation.

A Novel Variant of Bartter's Syndrome

Bartter's syndrome, a rare disorder affecting the renal tubular potassium handling, is characterized by metabolic alkalosis, hypokalemia and renal salt wasting. Here we describe a patient with Bartter's syndrome with hitherto undescribed clinical features and also discuss the various possibilities leading to such variant of Bartter's syndrome.

[Pseudo-Bartter syndrome--2 cases]

Bartter syndrome represents the group of renal disturbances characterized by hypokaliemia and metabolic alkalosis. Some diseases could display hypokalemic metabolic alkalosis without primary tubular dysfunction. These disorders are called pseudo-Bartter syndrome. In this paper we present 2 cases of pseudo-Bartter syndrome related among to other things to overuse of diuretic drugs.

Antenatal Bartter's syndrome: why is this not a lethal condition?

There are four themes in this teaching exercise for Professor McCance. The first challenge was to explain how a premature infant with Bartter's syndrome could survive despite having such a severe degree of renal salt wasting. Second, the medical team wanted to know why there was such a dramatic decrease in the natriuresis in response to therapy, despite the presence of a permanent molecular defect that affected the loop of Henle. Third, Professor McCance was asked why this patient seemed to have a second rare disease, AQP2 deficiency type of nephrogenic diabetes insipidus. The fourth challenge was to develop a diagnostic test to help the parents of this baby titrate the dose of indomethacin to ensure an effective dose while minimizing the likelihood of developing nephrotoxicity. The missing links in this interesting story emerge during a discussion between the medical team and its mentor.

[Bartter syndrome and it's neonatal type]

For the first time neonatal variant of Bartter syndrome to 14.5-year old girl is presented in Lithuania. It is a rare genetical disease with autosomal recessive inheritance. The patient was born prematurely, had polyhydramnion, polyuria and polydypsia, a craving for salt, specific outlook and was mentally retarded, had muscle weakness and nephrocalcinosis. Hypokalemia, hyperreninemia and metabolic alkalosis were found. Urine analysis revealed impaired renal concentration capacity, hypercalciuria and hypernatriuria. She had the symptom of systemic disease - osteopenia. Literature review on Bartter's syndrome is done.

Novel SLC12A1 (NKCC2) mutations in two families with Bartter syndrome type 1

Bartter syndrome (BS) type 1, also referred to antenatal BS, is a genetic tubulopathy with hypokalemic metabolic alkalosis and prenatal onset of polyuria leading to polyhydramnios. It has been shown that BS type 1 is caused by mutations in the SLC12A1 gene encoding bumetanide-sensitive Na-K-2Cl (-) cotransporter (NKCC2). We had the opportunity to care for two unrelated Japanese patients of BS type 1 with typical manifestations including polyhydramnios, prematurity, hypokalemia, alkalosis, and infantile-onset nephrocalcinosis. Analysis of the SLC12A1 gene demonstrated four novel mutations: N117X, G257S, D792fs and N984fs. N117X mutation is expected to abolish most of the NKCC2 protein, whereas G257, which is evolutionary conserved, resides in the third transmembrane domain. The latter two frameshift mutations reside in the intra-cytoplasmic C-terminal domain, which illustrates the importance of this domain for the NKCC2 function. In conclusion, we found four novel SLC12A1 mutations in two BS type 1 patients. Development of effective therapy for hypercalciuria is mandatory to prevent nephrocalcinosis and resultant renal failure.

Option of pre-emptive nephrectomy and renal transplantation for Bartter's syndrome

Bartter's syndrome (BS) is an incurable genetic disease, with variable response to supportive therapy relating to fluid and electrolyte management. Poor control or therapy non-compliance may result in frequent life threatening episodes of dehydration, acidosis and hypokalemia, with resultant adverse effects on patient quality of life (QOL). We report, for the first time, pre-emptive bilateral native nephrectomies and successful renal transplantation, prior to the onset of ESRD, for severe, clinically brittle, neonatal BS, resulting in correction of metabolic abnormalities and excellent graft function. We propose that fragile BS should be considered as a possible indication for early native nephrectomies and pre-emptive renal transplantation, procedures that results in a 'cure' for the underlying disease and significant improvements in patient QOL.

[Bartter's syndrome and Gitelman's syndrome: Pathogenesis, pathophysiology, and therapy]

Bartter's syndrome was reported in 1962, and Gitelman's syndrome, which is subtype of Bartter's syndrome was described later. These syndromes are characterized by hypokalemia, hypochloremic metabolic alkalosis, normal to low blood pressure, although they show hyperreninemia, and hyperaldosteronemia. The cause of these diseases have been unexplained for a long time. Recently however, from 1996 to 2002, several causes have identified. Bartter's syndrome can occur due to a loss of function mutation in NKCC2, ROMK, CLC-Kb and barttin, or a gain of function mutation of calcium-sensing receptor. Gitelman's syndrome can occur due to a loss of function mutation in NCC. Different causes need different treatment and have different prognosis. In fact, we cannot examine all DNA sequences in regular hospitals. So it is our goal to make a clinical diagnostic standard to appropriate treatment.

Perinatal management of a preterm neonate affected by hyperprostaglandin E2 syndrome (HPS)

BACKGROUND

Neonates affected by hyperprostaglandin E(2) syndrome (HPS) present with severe polyuria. Both urinary losses as well as prostaglandin synthesis inhibitors may precipitate acute renal failure (ARF).

AIM

Our goal was to maintain euvolaemia by replacement of urinary losses.

PATIENT

Our patient was born prematurely with a family history typical of HPS. Urinary salt and water losses and PGE(2) excretion were determined in 2- to 4-h intervals. Salt and water were replaced accordingly.

RESULTS

Within the first 48 h, urinary losses and PGE(2) increased continuously to 50 ml/kg/h and 374 ng/h/1.73 m(2), respectively. Following exposure to 0.05-0.5 mg/kg/d indomethacin, urinary output decreased steadily to 10-15/ml/kg/h.

CONCLUSION

In euvolaemic preterm neonates with HPS and the need for excessive replacement of salt and water, inhibition of renal PGE(2) excretion with indomethacin effectively reduces polyuria and natriuresis without acutely compromising renal function.

Clinical features and treatment approaches in cystic fibrosis with pseudo-Bartter syndrome

INTRODUCTION

Infants with cystic fibrosis (CF) are prone to develop episodes of hyponatraemic, hypochloraemic dehydration with metabolic alkalosis, which are biochemical hallmarks of the pseudo-Bartter syndrome (PB).

METHOD

We reviewed the clinical and laboratory features and treatment approaches of 29 children with CF and PB who were under follow-up in our institution from May 1992 to November 2003.

RESULTS

Of 241 patients with CF, PB was detected in 29 (12%) with a median age of 4 months at the time of the first attack. Most patients experienced vomiting, loss of appetite and dehydration during episodes of PB. All patients were managed with intravenous fluids and sodium chloride solutions. During follow-up, 12/29 cases required hospital admission for recurrent PB attacks. The oldest age at the time of the last attack was 48 months.

CONCLUSIONS

CF should be considered in the differential diagnosis of metabolic alkalosis in young children. Vomiting and loss of appetite are important warning signs of possible PB in CF patients, particularly before 4 years of age. To prevent serious complications, it is crucial that parents and physicians recognise PB as early as possible.

A simple and rapid approach to hypokalemic paralysis

Hypokalemia with paralysis (HP) is a potentially reversible medical emergency. It is primarily the result of either hypokalemic periodic paralysis (HPP) caused by an enhanced shift of potassium (K(+)) into cells or non-HPP resulting from excessive K(+) loss. Failure to make a distinction between HPP and non-HPP could lead to improper management. The use of spot urine for K(+) excretion rate and evaluation of blood acid-base status could be clinically beneficial in the diagnosis and management. A very low rate of K(+) excretion coupled with the absence of a metabolic acid-base disorder suggests HPP, whereas a high rate of K(+) excretion accompanied by either metabolic alkalosis or metabolic acidosis favors non-HPP. The therapy of HPP requires only small doses of potassium chloride (KCl) to avoid rebound hyperkalemia. In contrast, higher doses of KCl should be administered to replete the large K(+) deficiency in non-HPP.

Bartter syndrome

PURPOSE OF REVIEW

This review describes recent advances in our understanding of the genetic heterogeneity, pathophysiology and treatment of Bartter syndrome, a group of autosomal recessive disorders that are characterized by markedly reduced or absent salt transport by the thick ascending limb of Henle. Consequently, individuals with Bartter syndrome exhibit renal salt wasting and lowered blood pressure, hypokalemic metabolic alkalosis and hypercalciuria with a variable risk of renal stones.

RECENT FINDINGS

Previously, three genes (SLC12A2, the sodium-potassium-chloride co-transporter; KCNJ1, the ROMK potassium ion channel; ClC-Kb, the basolateral chloride ion channel) had been identified as causing antenatal and 'classic' Bartter syndrome. Two additional genes have now been identified. Barttin is a beta-subunit that is required for the trafficking of CLC-K (both ClC-Ka and ClC-Kb) channels to the plasma membrane in both the thick ascending limb and the marginal cells in the scala media of the inner ear that secrete potassium ion-rich endolymph. Loss-of-function mutations in barttin thus cause Bartter syndrome with sensorineural deafness. In addition, severe gain-of-function mutations in the extracellular calcium ion-sensing receptor can result in a Bartter phenotype because activation of this G protein-coupled receptor inhibits salt transport in the thick ascending limb (a furosemide-like effect).

SUMMARY

Five genes have been identified as causing Bartter syndrome (types I-V), with the unifying pathophysiology being the loss of salt transport by the thick ascending limb. Phenotypic differences in Bartter types I-V relate to the specific physiological roles of the individual genes in the kidney and other organ systems.

[Bartter's syndrome--hypokalemic renal tubular syndrome]

Hypokalemia is associated with some renal diseases manifested by renal tubular acidosis (type I and II) or by renal tubular syndrome (Bartter's, Gitelman's and Liddle's syndrome). Bartter's syndrome, originally described by Batter and colleagues in 1962, is a set of closely related renal tubular disorders characterized by hypokalemia, hypochloremia, metabolic alkalosis and hyperreninemia with normal blood pressure. The underlying renal abnormality results in excessive urinary losses of sodium, chloride, potassium and calcium. Muscle weakness, polydipsia, polyuria and mental retardation can be also present. Affected children have poor growth rates and they appear malnourished. The article is focused on ethiopathogenesis, laboratory and clinical characteristics and on the treatment of Bartter's syndrome.

Hypokalemic metabolic alkalosis--three case reports

The two most common forms of inherited normotensive hypokalemic metabolic alkalosis are Bartter's and Gitelman's syndromes. Bartter's syndrome typically present with normal or increased calcium excretion. Hypomagnesemia occurs in only one third of affected individuals. In contrast, hypomagnesemia and hypocalciuria are considered hallmarks of Gitelman's syndrome. In most patients, the symptom of muscle weakness and polyuria occur early in life, which may be attributed to potassium depletion. Despite hyperaldosteronism, the patients tend to be normotensive, which is at least explained by vascular hyperresponsiveness to prostaglandins. Therapeutic approaches to Bartter's and Gitelman's syndromes include potassium supplementation, prostaglandin synthesis inhibitors (nonsteroid anti-inflammatory agents), aldosterone antagonists and converting enzyme inhibitors. Three patients with hypokalemia, normal blood pressure, metabolic alkalosis, hyperreninemia and hyperaldosteronism are described. Two patients had Bartter's syndrome and one patients had Gitelman's syndrome.

Chronic renal failure, end-stage renal disease, and peritoneal dialysis in Gitelman's syndrome

The chronic state of hypovolemia, hypotension, and hypokalemia found in Bartter's syndrome has been shown to lead to a chronic nephropathy, which then can progress toward end-stage renal disease and dialysis. This progression, however, has never been reported for Gitelman's syndrome, a variant of Bartter's syndrome that shows a milder clinical picture. This report is the first to document this progression (ie, the development of end-stage renal disease in Gitelman's syndrome) as well as the first report of the use of peritoneal dialysis in either Bartter's syndrome or Gitelman's syndrome. The clinical course highlights the importance of and the need for careful control of hemodynamic status in these patients to slow the progression of renal injury. The hemodynamic alterations that characterize Bartter's syndrome and Gitelman's syndrome patients suggest that for patients requiring renal replacement therapy, peritoneal dialysis is a more appropriate treatment because of its less severe impact on these parameters.

[Pseudo-Gitelman's syndrome as consequence of loop diuretics abuse]

We describe a case of 40-year old patient with chronic, resistant to treatment hypokalaemia. Differential diagnosis of renal potassium loss among Gitelman's syndrome, Bartter's syndrome and loop diuretic abuse was made.

[Bartter's syndrome: new classification, old therapy]

We report on two cases of Bartter's syndrome, together with the review of current literature on the aetiology, development and treatment of Bartter's syndrome. Bartter's syndrome belongs to a group of hypokalaemic renal channelopathies, which are caused by a molecular hereditary disorder of ion channels in renal tubules. These channels are located in the lipid layer of cell membranes where they exist as water channels through which ion transport is performed. Based on the type of genetic disorder and clinical presentation, Bartter's syndrome is classified as neonatal, classical and Gitelman's syndrome. Neonatal form is found in newborns and is characterized by foetal polyuria, premature birth, postnatal episodes of severe dehydration, growth retardation, hypercalciuria and early nephrocalcinosis. It is the result of mutation of a gene responsible for renal tubular Na-K-2Cl cotransport or another gene which controls the ATP-dependant potassium channel (ROMK). Classic form is found in young children with polyuria, hypokalaemia and growth retardation. This type is caused by a defect of a gene for chloride channel (CIC-Kb) in the distal tubule. Gitelman's syndrome is found in late childhood or adolescence. It is caused by mutation in the gene for Na-Cl co-transport in the distal tubule. Children with Gitelman's syndrome occasionally have muscle weakness or tetany, hypokalaemia and hypomagnesaemia. Even though there have been advances in understanding the aetiology and pathogenesis of Bartter's syndrome in the recent years, the possibilities and strategies for its management remained almost the same. Treatment is based on prostaglandin inhibitors, potassium sparing diuretics and substitution therapy.

Bartter syndrome: an overview

The term Bartter syndrome denotes a group of renal diseases which share a common denominator of hypokalaemia and metabolic alkalosis. The patch-clamp technique has made possible the analysis of single ion channels, improving our understanding of the molecular physiopathology of all the 'Bartter-like' syndromes. Genetic mapping of each defect has further clarified the mutations involved and the possible modes of inheritance. This improved understanding has opened new avenues for therapy, improving mortality and morbidity in these patients. Another group of illnesses, the 'pseudo-Bartter syndrome', may produce a hypokalaemic metabolic alkalosis without primary renal disease. The underlying illness needs to be identified and treated.

[Bartter's syndromes]

Bartter syndromes are defined as a family of inherited recessive autosomal tubulopathies. They are characterized by hypochloremia, hypokalemia, metabolic alkalosis associated with potassium renal leakage and normal blood pressure despite increased plasma renin activity. Three forms of the disease are identified as followed: 1) Gitelman syndrome or hypocalciuria hypomagnesemia syndrome is a mild form often discovered in childhood or teenagers in reason of tetany. It is an homogeneous disorder related to mutations of the genes encoding the thiazide-sensitive Na-Cl cotransporter located in the distal convoluted tubule. 2) Antenatal Bartter syndrome with hypercalciuria and nephrocalcinosis or hyperprostaglandin E syndrome is a severe form, often revealed by hydramnios, prematurity and growth delay. It is related to mutations of two types of genes encoding for transporters of Henle's loop: the bumetanide-sensitive cotransporter Na-K-2Cl (NKCC2) [type I] or the inwardly-rectifying potassium channel (ROMK) [type II]. 3) the classical form or type III Bartter syndrome, often revealed by dehydration in the first year of life, is associated with hypomagnesemia in 20% of cases and normal or increased calciuria. This form is related to mutations of CLCNKB gene encoding for a chloride channel in Henle's loop. This classification, in part related to the demonstration of mutations in the genes encoding for tubular chloride or potassium channels, does not fit all cases, overlapping syndromes are frequent. Moreover some endocrinological (diabetes) and neurological (deafness) abnormalities are sometimes associated with Bartter syndromes. Both phenotypic and genetic approach must help to the diagnosis of these tubulopathies.

Recombinant human growth hormone and Gitelman's syndrome

Gitelman's syndrome is a primary renal tubular disorder with hypokalemic metabolic alkalosis, hypocalciuria, and magnesium deficiency. Short stature is one of clinical manifestations in children. The pathogenesis of short stature in Gitelman's syndrome is not known. To evaluate whether growth hormone (GH) is deficient and whether recombinant human GH (rhGH) improves growth rate, rhGH therapy was tried in a child with Gitelman's syndrome. Both height and body weight were less than the third percentile. Laboratory and radiologic findings suggested GH deficiency. During the first 6 months, rhGH therapy with potassium supplement markedly elevated growth rate from 3.8 cm/yr to 12.0 cm/yr. After cessation of rhGH, height increment markedly decreased to the pretreatment level of 3.6 cm/yr during the second 6 months. Additionally, hypomagnesemia was corrected after rhGH therapy. Accordingly, GH deficiency may contribute to short stature in children with Gitelman's syndrome, and rhGH therapy would be an excellent adjunctive treatment for short children with Gitelman's syndrome whose condition is resistant to conventional therapies in terms of growth.

Functional consequences of ROMK mutants linked to antenatal Bartter's syndrome and implications for treatment

The antenatal variant of Bartter's syndrome is an autosomal recessive kidney disease characterized by polyhydramnios, premature delivery, hypokalemic alkalosis and hypercalciuria. It is genetically heterogeneous, having been linked recently to mutations in an ATP-sensitive, renal outer medullary K+channel, ROMK, and earlier to mutations in the Na-K-2Cl co-transporter, NKCC2. We characterized four of the mutations reported in three heterozygous ROMK variants of antenatal Bartter's and found that each expressed a distinct phenotype in Sf9 cells. One mutation expressed normal function and appears to be an allelic polymorphism. The other three mutations produced channels with significantly reduced K+fluxes. However, the mechanisms in each case were different and reflected abnormalities in phosphorylation, proteolytic processing or protein trafficking. The different mechanisms may be important in the design of appropriate therapy for patients with this disease.

Bartter and related syndromes: the puzzle is almost solved

It is now evident that the term Bartter syndrome does not represent a unique entity but encompasses a variety of disorders of renal electrolyte transport. Application of molecular biology techniques has permitted a better understanding of these "Bartter-like syndromes," which at present can be divided into three different genetic and clinical entities. Neonatal Bartter syndrome is observed in newborn infants and characterized by polyhydramnios, premature delivery, life-threatening episodes of fever and dehydration during the early weeks of life, growth retardation, hypercalciuria, and early-onset nephrocalcinosis. Two molecular defects have been identified: either at the gene encoding the renal bumetanide-sensitive Na-K-2Cl cotransporter (NKCC2) or the gene encoding an ATP-sensitive inwardly rectifying K channel (ROMK). "Classic" Bartter syndrome is mostly observed during infancy and childhood and is characterized clinically by polyuria and growth retardation. Nephrocalcinosis is not present. Very recently, either deletions or mutations at the gene encoding a renal chloride channel (ClC-Kb) have been identified. Gitelman syndrome is observed in older children and adults presenting with intermittent episodes of muscle weakness and tetany, hypokalemia, and hypomagnesemia. Mutations at the gene encoding the thiazide-sensitive Na-Cl cotransporter have been identified in the majority of patients studied. Obviously the validity of this classification must be confirmed in the near future when all mutations have been described and genotypic-phenotypic correlations are better defined.

Renal potassium wasting and hypocalciuria ameliorated with magnesium repletion in Gitelman's syndrome

A woman aged 45 years was presented with hypokalemic metabolic alkalosis and hypomagnesemia associated with renal potassium and magnesium wasting. Her 24-hour urinary calcium excretion was strikingly low despite normocalcemia and normal creatinine clearance, which is one of characteristic findings of Gitelman's syndrome (GS). She was evaluated for the responses following Mg supplementation for 10 days, which showed marked increments in serum potassium and magnesium as well as improvements of the degree of renal potassium wasting and hypocalciuria. This amelioration of abnormal biochemical pictures in this patient after Mg supplementation proposes that the hypokalemia with renal potassium wasting and hypocalciuria may be caused by abnormal Mg metabolism.

Bartter's syndrome, supraventricular tachycardia, mitral valve prolapse, and asthma: a therapeutic challenge

A 25-year-old man with acquired Bartter's syndrome, mitral valve prolapse, and supraventricular tachycardia secondary to a low atrial focus was diagnosed with asthma. The unique aspects of managing these coexisting diseases are evaluated. Calculation of free-water clearance in the diagnosis of Bartter's syndrome and the etiology and characteristics of the syndrome are discussed.

"Neonatal variant" of Bartter syndrome presenting with acidosis

An infant is reported with the "neonatal variant" of Bartter syndrome, presenting at 5 weeks of age with metabolic acidosis associated with a life-threatening water and electrolyte depletion. Alkalosis was first shown after 2 weeks of vigorous fluid, sodium, and potassium substitution. We suggest that the extreme fluid and electrolyte losses associated with the "neonatal form" of Bartter syndrome could lead to acidosis more often than previously suspected, and may cause underdiagnosis of a possibly fatal condition.

Anaesthetic management of a child with Bartter's syndrome

We report the anaesthetic management of an eight-year-old asthmatic boy with Bartter's syndrome who had bilateral orchidopexy with caudal epidural analgesia. Bartter's syndrome is a rare congenital disorder characterized by hypokalaemic hypochloraemic metabolic alkalosis, hyperaldosteronism, hyperreninaemia and hyperplasia of the juxtaglomerular apparatus of the kidneys. Characteristically, although these patients are normotensive they may be hypovolaemic. They may have unstable baroreceptor responses and show marked resistance to vasopressors. Hence, fluid, acid-base and electrolyte imbalances along with haemodynamic instability pose particular problems in their anaesthetic management. Previous case reports have described the management of these patients with general anaesthesia, our patient had his orchidopexy with caudal epidural analgesia using plain bupivacaine 0.5%. The patient was haemodynamically stable throughout surgery and was comfortable with caudal analgesia as the sole anaesthetic. Hypovalaemia, acid-base status and electrolyte imbalance were treated before instituting caudal epidural analgesia. We present this case report which describes the anaesthetic considerations in the light of the pathophysiology of Bartter's syndrome.

Acute muscular paralysis in an adult with subclinical Bartter's syndrome associated with gentamicin administration

We report an adult case of asymptomatic Bartter's syndrome with the first presentation of hypokalemic paralysis triggered by gentamicin injection. Marked hypokalemia and hypomagnesemia associated with excessive kaliuresis and magnesiuria were found. Plasma renin activity and aldosterone concentration were high, but blood pressure was normal. Renal biopsy revealed hypercellularity of the renin-producing cell of the juxtaglomerular apparatus. Muscular paralysis subsided after potassium chloride supplementation. Hypokalemia was corrected with potassium and magnesium supplements and the use of diclofenac. To the best of our knowledge, there have been no reports of muscular paralysis associated with gentamicin in Bartter's syndrome.

Unresolved issues in the pathogenesis of Bartter's syndrome and its variants

Recent physiologic information concerning the renal response to potassium deprivation has been used to reevaluate potassium wasting in Bartter's syndrome. Experimental patient data support the notion that failure of potassium conservation is due to an imbalance between tubular secretory and reabsorptive processes. Suggestions are presented for the further evaluation of potassium reabsorptive pathways in the distal tubule.

[Hypokalemia in the course of a Bartter syndrome]

We report on diagnostic and differential diagnostic considerations in the case of a 30 year old Italian woman with hypokalemic alkalosis, fatigue and muscular weakness. The symptoms were caused by a Bartter syndrome with distinctly increased renin but almost normal aldosterone levels in the serum and increased aldosterone values in the urine.

[Bartter syndrome]

Bartter's syndrome, sometimes a familial autosomal recessive condition, is characterized by hypokalaemia with normal kaliuresis, hyperreninaemia with secondary hyperaldosteronism, vascular resistance to angiotensin and overproduction of prostaglandins by the kidneys. This syndrome is rare but sometimes envisaged in patients with unexplained hypokalaemia, the main difficulty being to exclude intoxication with diuretics which is very similar in all respects. Its physiopathology is unknown, and the various hypotheses put forward since it was first described (vascular insensitiveness to angiotensin, defect of sodium or chloride reabsorption, excess of atrial natriuretic factor, general abnormality of membrane permeability) were unable to demonstrate their primary character, each disorder described seeming, subsequently, secondary to another. For this reason, treatment is difficult and disappointing, but although the hypokalaemia is sometimes worrying, Bartter's syndrome is usually a benign condition.