Management of potassium-wasting syndrome in the antepartum, intrapartum and postpartum period.

Potassium-wasting syndromes, including Gitelman or Bartter syndrome, require close medical and biochemical review during pregnancy to reduce potentially severe complications, morbidity and mortality. We report a case of severe potassium-wasting syndrome managed successfully in pregnancy with extremely high oral potassium intake.

Paradoxes in magnesium transport in type 1 Bartter's syndrome and Gitelman's syndrome: a modeling analysis.

Type 1 Bartter's syndrome and Gitelman's syndrome are characterized by mutations in two key renal Na+ transporters, Na-K-2Cl cotransporter (NKCC2) and Na-Cl cotransporter (NCC). Since these two transporters play an important role in regulating magnesium (Mg2+) and calcium (Ca2+) transport in the kidney, significant alterations in the transport of these two electrolytes are observed in type 1 Bartter's syndrome and Gitelman's syndrome. In this study, we used our sex-specific computational models of renal electrolyte transport in rats to understand the complex compensatory mechanisms, in terms of alterations in tubular dimensions and ion transporter activities, that lead to Mg2+ and Ca2+ preservation or wasting in these two genetic disorders. Given the sexual dimorphism in renal transporter patterns, we also assessed how the magnitude of these alterations may differ between males and females. Model simulations showed that in type 1 Bartter's syndrome, nephron adaptations prevent salt wasting and favor Mg2+ preservation but not Ca2+, whereas in Gitelman's syndrome, those adaptations favor Ca2+ preservation over Mg2+. In addition, our models predicted that the compensatory alterations in tubular dimensions and ion transporter activities are stronger in females than in males.NEW & NOTEWORTHY Although changes in Ca2+ excretion in type 1 Bartter's syndrome and Gitelman's syndrome are well understood, Mg2+ excretion displays an interesting paradox. This computational modeling study provides insights into how renal adaptations in these two disorders impact Ca2+ and Mg2+ transport along different nephron segments. Model simulations showed that nephron adaptations favor Mg2+ preservation over Ca2+ in Bartter's syndrome and Ca2+ preservation over Mg2+ in Gitelman's syndrome and are stronger in females than in males.

Clinical, genetic characteristics and outcome of four Chinese patients with Bartter syndrome type 3: Further insight into a genotype-phenotype correlation.

Aim: To investigate the characteristics of 4 Chinese patients with Bartter syndrome type 3 (BS Type 3). Methods: The clinical data, genetic analysis, and outcome of four cases with Bartter syndrome type 3 were retrospectively summarised. Results: Gene sequencing analysis showed that all children carried a compound heterozygous mutation in the CLCNKB gene and were diagnosed with BS type 3. All types of mutations were detected, including two missense mutations, one nonsense mutation, one small fragment deletion mutation, two large deletion mutations and one splice-site mutation. The splice-site mutation c.100 + 1 (IVS2) C > T was novel. Two cases carried large deletion mutations. The patients presented as classic BS with modest manifestations. The most common sign was growth retardation. There was no polyhydramnios or preterm delivery. All cases were treated with potassium chloride supplementation and indomethacin. During long-term follow-up, clinical symptoms and growth retardation improved significantly. Nephrocalcinosis or renal dysfunction was not observed. Conclusion: The clinical manifestations of BS type 3 are mostly presented as cBS. Growth retardation is a common sign. BS type 3 had a good long-term prognosis. There were various types of mutations in the CLCNKB gene. Large deletions were the most common.

X-linked transient antenatal Bartter syndrome related to MAGED2 gene: enriching the phenotypic description and pathophysiologic investigation.

PURPOSE: Transient Bartter syndrome related to pathogenic variants of MAGED2 is the most recently described antenatal Bartter syndrome. Despite its transient nature, it is the most severe form of Bartter syndrome in the perinatal period. Our aim was to describe 14 new cases and to try to explain the incomplete penetrance in women. METHODS: We report on 14 new cases, including 3 females, and review the 40 cases described to date. We tested the hypothesis that MAGED2 is transcriptionally regulated by differential methylation of its CpG-rich promotor by pyrosequencing of DNA samples extracted from fetal and adult leukocytes and kidney samples. RESULTS: Analysis of the data from 54 symptomatic patients showed spontaneous resolution of symptoms in 27% of cases, persistent complications in 41% of cases and fatality in 32% of cases. Clinical anomalies were reported in 76% of patients, mostly renal anomalies (52%), cardiovascular anomalies (29%) and dysmorphic features (13%). A developmental delay was reported in 24% of patients. Variants were found in all regions of the gene. Methylation analysis of the MAGED2 CpG-rich promotor showed a correlation with gender, independent of age, tissue or presence of symptoms, excluding a role for this mechanism in the incomplete penetrance in women. CONCLUSION: This work enriches the phenotypic and genetic description of this recently described disease, and deepens our understanding of the pathophysiological role and regulation of MAGED2. Finally, by describing the wide range of outcomes in patients, this work opens the discussion on genetic counseling offered to families.

[Two Cases of Pseudo-Bartter Syndrome in Childhood: When to Suspect a Rare Onset Pattern of Cystic Fibrosis].

Cystic fibrosis is a multisystem disease with extremely variable onset, symptoms and course. One of the onset modality but also a complication of the disease is the pseudo-Bartter syndrome, characterized by hyponatremia, hypochloremic dehydration and metabolic alkalosis in absence of any renal disease. This syndrome occurs more frequently in the first year of life and has a peak in the summer. In this article, we describe two cases of cystic fibrosis associated with pseudo-Bartter syndrome in childhood. Excluding every possible cause of metabolic alkalosis associated with hyponatremia was crucial for our diagnostic pathway, and the experience gained with the first case helped a lot with the second one.

Hypokalemia in a young man think Bartter syndrome type 3.

Background: Bartter syndrome is an autosomal recessive salt reabsorption disorder that results in decreased extracellular fluid volume with low/normal blood pressure. Case presentation: A 17-year-old boy with polydipsia, polyuria, weakness in the lower limbs, and ataxic gait. His Laboratory test shows hypokalemia; hypochloremia, hypomagnesemia and metabolic alkalosis. The authors' patient was managed by fluid and electrolyte replacement, which is essential in emergency management. Conclusion: Bartter syndrome is difficult to treat, and currently, there is no complete cure. The overall prognosis depends on the extent of receptor dysfunction, and despite these facts, most patients can live a normal life if they strictly follow their treatment plan.

Protein Quality Control of NKCC2 in Bartter Syndrome and Blood Pressure Regulation.

Mutations in NKCC2 generate antenatal Bartter syndrome type 1 (type 1 BS), a life-threatening salt-losing nephropathy characterized by arterial hypotension, as well as electrolyte abnormalities. In contrast to the genetic inactivation of NKCC2, inappropriate increased NKCC2 activity has been associated with salt-sensitive hypertension. Given the importance of NKCC2 in salt-sensitive hypertension and the pathophysiology of prenatal BS, studying the molecular regulation of this Na-K-2Cl cotransporter has attracted great interest. Therefore, several studies have addressed various aspects of NKCC2 regulation, such as phosphorylation and post-Golgi trafficking. However, the regulation of this cotransporter at the pre-Golgi level remained unknown for years. Similar to several transmembrane proteins, export from the ER appears to be the rate-limiting step in the cotransporter's maturation and trafficking to the plasma membrane. The most compelling evidence comes from patients with type 5 BS, the most severe form of prenatal BS, in whom NKCC2 is not detectable in the apical membrane of thick ascending limb (TAL) cells due to ER retention and ER-associated degradation (ERAD) mechanisms. In addition, type 1 BS is one of the diseases linked to ERAD pathways. In recent years, several molecular determinants of NKCC2 export from the ER and protein quality control have been identified. The aim of this review is therefore to summarize recent data regarding the protein quality control of NKCC2 and to discuss their potential implications in BS and blood pressure regulation.

[Cystic fibrosis primarily presenting with pseudo-Bartter syndrome: a report of three cases and literature review]. / 以假性Bartter综合征为主要表现的囊性纤维化患儿3ä¾‹å¹¶æ–‡çŒ®å¤ä¹ .

OBJECTIVES: To summarize the clinical characteristics and genetic variations in children with cystic fibrosis (CF) primarily presenting with pseudo-Bartter syndrome (CF-PBS), with the aim to enhance understanding of this disorder. METHODS: A retrospective analysis was performed on the clinical data of three children who were diagnosed with CF-PBS in Hunan Children's Hospital from January 2018 to August 2023, and a literature review was performed. RESULTS: All three children had the onset of the disease in infancy. Tests after admission showed hyponatremia, hypokalemia, hypochloremia, and metabolic alkalosis, and genetic testing showed the presence of compound heterozygous mutation in the CFTR gene. All three children were diagnosed with CF. Literature review obtained 33 Chinese children with CF-PBS, with an age of onset of 1-36 months and an age of diagnosis of 3-144 months. Among these children, there were 29 children with recurrent respiratory infection or persistent pneumonia (88%), 26 with malnutrition (79%), 23 with developmental retardation (70%), and 18 with pancreatitis or extrapancreatic insufficiency (55%). Genetic testing showed that c.2909G>A was the most common mutation site of the CFTR gene, with a frequency of allelic variation of 23% (15/66). CONCLUSIONS: CF may have no typical respiratory symptoms in the early stage. The possibility of CF-PBS should be considered for infants with recurrent hyponatremia, hypokalemia, hypochloremia, and metabolic alkalosis, especially those with malnutrition and developmental retardation. CFTR genetic testing should be performed as soon as possible to help with the diagnosis of CF.

Coronary artery bypass surgery in a patient with Bartter's syndrome - postoperative critical care management: a case report.

Bartter syndrome is a rare, renal tubulopathy caused by defective salt reabsorption in the thick ascending limb of the loop of Henle which results in salt wasting, hypokalemia, and metabolic disturbances. The electrolyte disturbances associated with this condition can be difficult to manage in the postoperative setting, especially in patients undergoing cardiac surgery. We report a case of a 62-year-old male with a history of diabetes, hypertension, coronary artery disease, and Bartter syndrome who underwent coronary artery bypass grafting and who developed severe lactic acidemia and severe electrolyte abnormalities postoperatively. Treatment consisted of aggressive resuscitation with crystalloid and intravenous (IV) electrolyte replacement.

"Every Cloud Has a Silver Lining": How Three Rare Diseases Defend Themselves from COVID-19 and What We Have Learnt from It.

The process of SARS-CoV-2 infection, responsible for the COVID-19 pandemic, is carried out through different steps, with the interaction between ACE2 and Spike protein (S) being crucial. Besides of that, the acidic environment of endosomes seems to play a relevant role in the virus uptake into cells and its intracellular replication. Patients affected by two rare genetic tubulopathies, Gitelman's and Bartter's Syndromes, and a rare genetic metabolic disease, Fabry Disease, have shown intrinsic protection from SARS-CoV-2 infection and COVID-19 on account of specific intrinsic features that interfere with the virus uptake into cells and its intracellular replication, which will be reported and discussed in this paper, providing interesting insights for present and future research.

AUP1 Regulates the Endoplasmic Reticulum-Associated Degradation and Polyubiquitination of NKCC2.

Inactivating mutations of kidney Na-K-2Cl cotransporter NKCC2 lead to antenatal Bartter syndrome (BS) type 1, a life-threatening salt-losing tubulopathy. We previously reported that this serious inherited renal disease is linked to the endoplasmic reticulum-associated degradation (ERAD) pathway. The purpose of this work is to characterize further the ERAD machinery of NKCC2. Here, we report the identification of ancient ubiquitous protein 1 (AUP1) as a novel interactor of NKCC2 ER-resident form in renal cells. AUP1 is also an interactor of the ER lectin OS9, a key player in the ERAD of NKCC2. Similar to OS9, AUP1 co-expression decreased the amount of total NKCC2 protein by enhancing the ER retention and associated protein degradation of the cotransporter. Blocking the ERAD pathway with the proteasome inhibitor MG132 or the α-mannosidase inhibitor kifunensine fully abolished the AUP1 effect on NKCC2. Importantly, AUP1 knock-down or inhibition by overexpressing its dominant negative form strikingly decreased NKCC2 polyubiquitination and increased the protein level of the cotransporter. Interestingly, AUP1 co-expression produced a more profound impact on NKCC2 folding mutants. Moreover, AUP1 also interacted with the related kidney cotransporter NCC and downregulated its expression, strongly indicating that AUP1 is a common regulator of sodium-dependent chloride cotransporters. In conclusion, our data reveal the presence of an AUP1-mediated pathway enhancing the polyubiquitination and ERAD of NKCC2. The characterization and selective regulation of specific ERAD constituents of NKCC2 and its pathogenic mutants could open new avenues in the therapeutic strategies for type 1 BS treatment.

Adult classic Bartter syndrome: a case report with 5-year follow-up and literature review.

Bartter syndrome (BS) is a rare, inherited salt-losing renal tubular disorder characterized by secondary hyperaldosteronism, hypokalemia, hypochloremia, metabolic alkalosis, and low-to-normal blood pressure. Classic BS, or BS Type 3, the most common subtype in the Asian population, is caused by a molecular defect in ClC-Kb, a voltage-gated chloride channel in renal tubules, due to CLCNKB gene mutation. Because the onset of BS is more common in children than in adults, the diagnosis, treatment outcomes, genotype/phenotype association, and follow-up of adult-onset BS Type 3 are limited. This case report describes the findings in a 20-year-old man who was admitted with hypokalemic paralysis, with clinical manifestations were similar to those of Gitelman syndrome (GS); however, the patient was later diagnosed to have BS Type 3 through genetic testing (NM_000085.4 (CLCNKB): c.1052G>T). A literature review showed that no homozygous mutations have been reported to date. After 5 years of treatment and follow-up, we found that this genotype requires high levels of potassium and is prone to urinary protein and metabolic syndrome. Distinguishing adult-onset BS from GS is challenging in clinical practice. However, genetic diagnosis can help solve this problem effectively, and genotypes play a guiding role in treatment planning.

Bartter syndrome in a female infant: A rare case report from Syria.

Antenatal Bartter syndrome is a rare condition that affects approximately 1.2 individuals per million. It is caused by renal tubular dysfunction that impairs the reabsorption of sodium and chloride. This results in various symptoms such as polyuria, vomiting, dehydration, and failure to thrive. Because of its low prevalence, diagnosing this disorder can be challenging for medical professionals. In this report, we describe a rare case of a 3-month-old female infant who had symptoms of Bartter syndrome, such as severe hypotension, facial flattening, cough, and seizures. She also had the typical features of the condition, except for prematurity and hypercalciuria, which were not present. In this case, we highlight the importance of regular follow-ups and monitoring of patients with dehydration and electrolyte imbalances, as these can lead to complications in Bartter syndrome. Early intervention and close monitoring can enhance patient outcomes and avoid complications.

Identification of a novel intronic mutation of MAGED2 gene in a Chinese family with antenatal Bartter syndrome.

BACKGROUND: Antenatal Bartter syndrome is a life-threatening disease caused by a mutation in the MAGED2 gene located on chromosome Xp11. It is characterized by severe polyhydramnios and extreme prematurity. While most reported mutations are located in the exon region, variations in the intron region are rarely reported. METHODS: In our study, we employed whole exome sequencing and Sanger sequencing to genotype members of this family. Additionally, a minigene assay was conducted to evaluate the impact of genetic variants on splicing. RESULTS: Our findings reveal a novel intronic variant (NM_177433.3:c.1271 + 4_1271 + 7delAGTA) in intron 10 of the MAGED2 gene. Further analysis using the minigene assay demonstrated that this variant activated an intronic cryptic splice site, resulting in a 96 bp insertion in mature mRNA. CONCLUSIONS: Our results indicate that the novel intronic variant (c.1271 + 4_1271 + 7delAGTA) in intron 10 of the MAGED2 gene is pathogenic. This expands the mutation spectrum of MAGED2 and highlights the significance of intronic sequence analysis.

ClC-K Kidney Chloride Channels: From Structure to Pathology.

The molecular basis of chloride transport varies all along the nephron depending on the tubular segments especially in the apical entry of the cell. The major chloride exit pathway during reabsorption is provided by two kidney-specific ClC chloride channels ClC-Ka and ClC-Kb (encoded by CLCNKA and CLCNKB gene, respectively) corresponding to rodent ClC-K1 and ClC-K2 (encoded by Clcnk1 and Clcnk2). These channels function as dimers and their trafficking to the plasma membrane requires the ancillary protein Barttin (encoded by BSND gene). Genetic inactivating variants of the aforementioned genes lead to renal salt-losing nephropathies with or without deafness highlighting the crucial role of ClC-Ka, ClC-Kb, and Barttin in the renal and inner ear chloride handling. The purpose of this chapter is to summarize the latest knowledge on renal chloride structure peculiarity and to provide some insight on the functional expression on the segments of the nephrons and on the related pathological effects.

Mitochondrial Dysfunction in Kidney Tubulopathies.

Mitochondria play a key role in kidney physiology and pathology. They produce ATP to fuel energy-demanding water and solute reabsorption processes along the nephron. Moreover, mitochondria contribute to cellular health by the regulation of autophagy, (oxidative) stress responses, and apoptosis. Mitochondrial abundance is particularly high in cortical segments, including proximal and distal convoluted tubules. Dysfunction of the mitochondria has been described for tubulopathies such as Fanconi, Gitelman, and Bartter-like syndromes and renal tubular acidosis. In addition, mitochondrial cytopathies often affect renal (tubular) tissues, such as in Kearns-Sayre and Leigh syndromes. Nevertheless, the mechanisms by which mitochondrial dysfunction results in renal tubular diseases are only scarcely being explored. This review provides an overview of mitochondrial dysfunction in the development and progression of kidney tubulopathies. Furthermore, it emphasizes the need for further mechanistic investigations to identify links between mitochondrial function and renal electrolyte reabsorption.

Recurrent transient severe hypocalcaemia in two siblings with type 1 Bartter syndrome.

Type 1 Bartter syndrome causes hypokalaemia and metabolic alkalosis owing to mutation in the SLC12A1 gene. Meanwhile, hypocalcaemia is rare in Bartter syndrome, except in type 5 Bartter syndrome. Herein, we describe two siblings with type 1 Bartter syndrome with recurrent transient severe hypocalcaemia. They each visited our hospital several times with chief complaints of numbness in the limbs, shortness of breath and tetany after stresses such as exercise or fever. Severe hypocalcaemia was also observed with a serum calcium level of approximately 6.0 mg/dL at each visit. The clinical symptoms and abnormalities in laboratory findings quickly improved with rest and intravenous treatment. In a steady state, no severe hypocalcaemia was evident, but serum intact parathyroid hormone (PTH) levels were high. In recent years, a large-scale study has revealed that type 1 and type 2 Bartter syndrome have high PTH values. In addition, there are reports that these patients develop hypocalcaemia due to PTH resistance. Therefore, our patient was also in a PTH-resistant state, and hypocalcaemia was thought to be exacerbated by physical stress. It is not well known that Bartter syndrome patients other than those with type 5 suffer from hypocalcaemia. And hypocalcaemia was not detected in normal examinations under steady-state conditions. Therefore, in patients with type 1 and type 2 Bartter syndrome, severe hypocalcaemia may occur, but may go unnoticed. When following up these patients, the attending physician must keep in mind that such patients are in a PTH-resistant state and that physical stress can cause severe hypocalcaemia.

A Case of Childhood-Onset Bartter Syndrome Type 1 with Renal Dysfunction / 罕见病研究

Bartter syndrome (BS, OMIM #601678) is a rare inherited salt-losing tubulopathy characterized by hypokalemia metabolic alkalosis with secondary renin-angiotensin-aldosterone system activation. As reported, BS type 1 is generally presented prenatal and neonatal period, and symptoms usually appear before and after birth or in infancy, accompanied by severe salt loss, whilst kidney function remains mostly normal. In this study, we report a case of BS type 1 with childhood onset and proteinuria and renal impairment. The child was born preterm due to hyperamniotic fluid, but there were no apparent symptoms after birth until the age of 3 when the child began to present with polydipsia, polyuria and increased nocturnal uria. At the age of 5, she had elevated serum creatinine level and proteinuria. After admission, she was diagnosed with chronic tubulointerstitial disease and stage 2 chronic kidney disease(CKD). According to the chloride clearance test, the abnormal function of medullary thick ascending limb Henle′s loop, was confirmed and BS type 1 was diagnosed by gene sequencing. After active management of complications, kidney function of the child improved. In the long-term follow-up, the urinary protein amount of the child still increased, eGFR slowly decreased, and the child was currently in the CKD2 stage. Children with prenatal BS may not present typical clinical manifestations immediately after birth until the onset of relevant clinical symptoms in childhood. BS type 1 patients may have renal impairment, which needs to be identified in time. Clinical differentiation diagnosis between BS and Gitelman syndrome can be made by chloride clearance tests. Early diagnosis and treatment are critical to improve prognosis.

Expert Consensus for the Diagnosis and Treatment of Bartter Syndrome in China(2023) / 罕见病研究

@#<p>Bartter syndrome (BS) is a rare inherited salt-losing renal tubular disorder characterized by secondary hyperaldosteronism with hypokalemia and hypochloremic metabolic alkalosis, and normal or low blood pressure. In severe cases, preterm delivery, hypovolemia, ventricular arrhythmia, rhabdo-myolysis, renal failure, growth failure and sensorineural deafness may occur. In recent years, research on BS has made significant progress. The Bartter Syndrome Consensus Working Group has performed a systematic literature review, and based on evidence-based medicine, summarized aspects related to BS, including clinical manifestations and classification, diagnosis, treatment strategies, and management of complications. This consensus provides an important reference for the better diagnosis and treatment of BS.</p>

A Case of Childhood-Onset Bartter Syndrome Type 1 with Renal Dysfunction / 罕见病研究

Bartter syndrome (BS, OMIM #601678) is a rare inherited salt-losing tubulopathy characterized by hypokalemia metabolic alkalosis with secondary renin-angiotensin-aldosterone system activation. As reported, BS type 1 is generally presented prenatal and neonatal period, and symptoms usually appear before and after birth or in infancy, accompanied by severe salt loss, whilst kidney function remains mostly normal. In this study, we report a case of BS type 1 with childhood onset and proteinuria and renal impairment. The child was born preterm due to hyperamniotic fluid, but there were no apparent symptoms after birth until the age of 3 when the child began to present with polydipsia, polyuria and increased nocturnal uria. At the age of 5, she had elevated serum creatinine level and proteinuria. After admission, she was diagnosed with chronic tubulointerstitial disease and stage 2 chronic kidney disease(CKD). According to the chloride clearance test, the abnormal function of medullary thick ascending limb Henle′s loop, was confirmed and BS type 1 was diagnosed by gene sequencing. After active management of complications, kidney function of the child improved. In the long-term follow-up, the urinary protein amount of the child still increased, eGFR slowly decreased, and the child was currently in the CKD2 stage. Children with prenatal BS may not present typical clinical manifestations immediately after birth until the onset of relevant clinical symptoms in childhood. BS type 1 patients may have renal impairment, which needs to be identified in time. Clinical differentiation diagnosis between BS and Gitelman syndrome can be made by chloride clearance tests. Early diagnosis and treatment are critical to improve prognosis.