Clinical Features and Unusual Heterozygous Mutations in Patients with Renal Hypokalemia.

BACKGROUND: Renal hypokalemia is associated with mutation. This study aimed to investigate the clinical features and pathogenic mutations in patients with renal hypokalemia. METHODS: The patients with hypokalemia were enrolled, and the renal function, thyroid function, renin-aldosterone system, urinary potassium excretion, and exome sequencing were performed. The correlation between the clinical phenotypes and causative genes was assessed. RESULTS: Five patients with hypokalemia were enrolled and diagnosed as tubular hypokalemia. The patients with common clinical manifestations were difficult to differentiate based on atypical laboratory findings. The results of the genetic analysis were as follows: both patient 1 and patient 2 were heterozygous for the c.C625T mutation of the KCNJ1 gene, which is responsible for Bartter syndrome. Patient 3 was heterozygous for the c.G298A mutation of the ATP6V1B1 gene, which is responsible for renal tubular acidosis. Patient 4 had a compound heterozygous mutation of c.G893A of the BSND gene, responsible for Bartter syndrome, and c.1029+5G>A, the ATP6V0A4 gene responsible for distal renal tubular acidosis. Patient 5 had Gitelman syndrome and carried the compound heterozygous mutations c.C1963T and c.G2029A of the SLC12A3 gene. All the above loci were known heterozygous mutations. CONCLUSIONS: The unusual heterozygous mutations were identified in five renal hypokalemia patients. Molecular diagnosis of tubular hypokalemia was conducive to accurate diagnosis and treatment.

An Unusual Case of Myoglobin Cast Nephropathy in a Patient with Bartter Syndrome: A Rare Entity.

A 5-year-old male child with complaints of failure to thrive (since 4 months of age) and developmental delay presented to the nephrology department with complaints of weakness in all four limbs for 5 days. On examination, he was hypotensive, dehydrated, and had reduced tone in all four limbs. Biochemistry revealed acute kidney injury (AKI), hyponatremia, hypocalcemia, and hypokalemia. Renal needle biopsy (in view of unexplained AKI) revealed ropy, granular pigment casts with marked tubular injury. Myoglobin stain was positive. The positive genetic analysis of the patient (CLCNKB gene) confirmed the clinical diagnosis of Bartter syndrome (BS). The child was managed with aggressive intravenous hydration with potassium and calcium supplementation, and AKI recovered.

A New Case Report of a CLCNKB Complex Heterozygous Mutation in Adult-Onset Type III Bartter Syndrome.

BACKGROUND: Type III Bartter syndrome (BS) is an autosomal recessive renal tubular disease caused by the mutation of the chloride voltage-gated channel Kb (CLCNKB) gene. This condition is characterized by renal sodium loss, hypokalemia, metabolic alkaliosis, high renin, and high aldosterone levels. METHODS: We report a case of adult type III BS caused by a novel complex heterozygous mutation of the CLCNKB gene. The peripheral blood was extracted for whole genome DNA extraction, and the genome exon region of BS- related genes, was predicted by high-throughput sequencing and protein function prediction software. The selected mutation sites were verified by sequencing with Sanger method. RESULTS: The new complex heterozygous mutations of CLCNKB include heterozygous deletion of exon 2 - 20 of CLCNKB and nonsense mutation of exon 19, c.2010G>A (p.W670X). This complex heterozygous mutation has not been reported in humans. CONCLUSIONS: For patients with high clinical suspicion of BS, a clear diagnosis should be made through genetic test-ing to improve patients' quality of life and provide genetic guidance.

[Two cases of Dent disease type 1 with Bartter-like phenotype and literature review].

The clinical presentation, treatment, and follow-up of two boys with type 1 Dent disease who exhibited a Bartter-like phenotype were retropectively analysed. The related literature of pediatric patients with type 1 Dent disease who had hypokalemia and metabolic alkalosis was screened through databases such as PubMed, CNKI, and Wanfang until February 1, 2024, and common features among these patients were summarized through literature review. A total of 7 literatures were included, and 9 children were included in the analysis. All patients were male, presenting with significant low molecular weight proteinuria and hypercalciuria. Other prominent characteristic phenotypes included short stature (7/8), hypophosphatemia (8/9), and rickets (6/8). Seven previously reported patients had missense or nonsense mutations, while 2 patients in this study carried possible pathogenic mutations in the CLCN5 gene, c.315+2T>A (p.?) and c.584dupT (p.I196Yfs*6), respectively. Five patients were able to maintain blood potassium levels around 3 mmol/L with oral potassium chloride solution combined with non-steroidal anti-inflammatory drugs (ibuprofen or indomethacin). The follow-up showed that 2 patients developed chronic kidney disease stage 4 and stage 3 at the age of 13 and 21 years, respectively. The phenotypic overlap between Dent disease and Batter syndrome is considerable,with the distinguishing feature being the presence of significant low molecular weight proteinuria. Patients with type 1 Dent disease presenting with the Bartter-like phenotype have a high prevalence of short stature, hypophosphatemia, and rickets. Non-steroidal anti-inflammatory drugs can be used to correct hypokalemia in patients under periodic renal function assessment.

Bartter Syndrome Presenting as Arginine-Vasopressin Resistance: A Report of 2 Cases.

BACKGROUND Bartter syndrome is a rare, inherited salt-wasting tubulopathy caused by mutations in 1 of 6 genes that express ion transport channels in the thick ascending limb of nephrons. Excessive prostaglandin E2 and associated hyperreninemic hyperaldosteronism occurs, causing polyhydramnios, polyuria, prematurity, failure to thrive, and characteristic physical features. Hypokalemia, hypochloremic metabolic alkalosis, and, depending on the affected gene, hypercalciuria and nephrocalcinosis are hallmarks of Bartter syndrome. CASE REPORT A 9-month-old male infant, born prematurely due to polyhydramnios, presented in the Emergency Department with dehydration due to incoercible vomiting and significant polyuria. A 6-year-old male infant with a previous history of prematurity due to polyhydramnios was referred to the Pediatric Endocrinology Department due to short stature and notable polydipsia and polyuria. Considering these marked symptoms, both cases triggered suspicion and started workup for arginine-vasopressin insufficiency/resistance. However, during the investigations, a broader clinical revision revealed that both had dysmorphic physical features (triangularly shaped face, prominent forehead, protruding ears, drooping mouth), poor growth, impaired weight gain, and typical biochemical findings (hypokalemic metabolic alkalosis, hypercalciuria, secondary hyperaldosteronism) of Bartter syndrome. Genetic testing confirmed the diagnosis of Bartter syndrome types 1 and type 2, respectively, and this diagnosis allowed proper treatment and significant clinical improvements, personalized follow-up, and genetic counseling for parents desiring further healthy pregnancies. CONCLUSIONS Here, we present clinical and follow-up findings of 2 patients with Bartter syndrome types 1 and 2 discovered upon a broader clinical revision of suspected arginine-vasopressin insufficiency/resistance. We also review pertinent data on diagnosis and management of this challenging syndrome.

[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.

Polymyxin B-induced Bartter syndrome.

Bartter syndrome is a genetic disorder characterised by chloride-unresponsive metabolic alkalosis, hypokalaemia, hypomagnesaemia and hypercalciuria. While it commonly presents antenatally or in early infancy, sometimes, drugs can induce a state similar to Bartter syndrome in any age group, called acquired Bartter syndrome. Polymyxins and aminoglycosides are the most commonly implicated drugs. Polymyxin B and polymyxin E (popularly known as colistin) are the two chemically similar polymyxins that are commonly used clinically. While colistin is frequently associated with nephrotoxicity, polymyxin B is generally considered less nephrotoxic. This difference is due to the way these two drugs are handled by the kidneys. In this case report, we discuss a middle-aged male who developed Bartter syndrome due to polymyxin B, which resolved on discontinuation of the drug, and re-appeared after its re-introduction later. This case exemplifies the nephrotoxicity caused by polymyxin B and the need for vigilance when using this drug.

[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.

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.

A case of pseudo-Bartter/Gitelman syndrome caused by long-term laxative abuse, leading to end-stage kidney disease.

Pseudo-Bartter/Gitelman syndrome (PBS/PGS) is a disorder that presents with hypokalemia and metabolic alkalosis resembling Gitelman syndrome (GS) due to secondary factors, such as lifestyle and /or medicines. Notably, PBS/PGS is more likely to cause renal dysfunction than GS. We report the first case of PBS/PGS due to long-term laxative abuse leading to end-stage kidney disease (ESKD). The patient was a 49-year-old woman with a history of constipation since school, who had used excessive doses of laxatives on her own judgment for nine years at least from 22 years of age. Two years later, blood tests revealed hypokalemia (serum K 3.1 mEq/L), and nine years later, the patient's renal function began to deteriorate (Cr-eGFR 48.7 mL/min/1.73 m2). Since abuse of laxatives was suspected as the cause, it was changed to the proper dosage of laxatives. At 33 years, the patient developed acute kidney injury (AKI), due to a urinary tract infection, and required intensive treatment, including hemodialysis. Although the patient was eventually weaned off dialysis, the renal function did not recover to pre-AKI levels. In suspected GS, comprehensive genetic testing for renal disease-related genes was performed; however, no obvious pathogenic variants were identified. Thereafter, despite decreasing the laxative doses and potassium supplementation, her renal function continued to decline. At 49 years, the patient developed ESKD and was started on maintenance hemodialysis. PBS/PGS is a disease that can lead to ESKD. An early diagnosis of PBS/PGS is crucial to prevent renal function deterioration, and the underlying causes should be removed immediately.

Bartter syndrome-like phenotype in a patient with type 2 diabetes mellitus.

Bartter syndrome (BS) is a rare genetic tubulopathy affecting the loop of Henle leading to salt wasting. It is commonly seen in utero or in the early neonatal period. Rare cases of acquired BS are reported in association with infections like tuberculosis, granulomatous conditions like sarcoidosis, autoimmune diseases and drugs. The mainstay of management includes potassium, calcium and magnesium supplementation. We report the case of a woman in her 50s with a history of type 2 diabetes mellitus for the last 10 years, who presented with diabetic foot ulcers and generalised weakness with ECG changes suggestive of hypokalaemia. She had severe hypokalaemia with high urine potassium excretion and hypochloraemic metabolic alkalosis. She poorly responded to intravenously administered potassium supplements and had persistent hypokalaemia. On further evaluation of the persistent hypokalaemia, a diagnosis of idiopathic Bartter-like phenotype was made. She responded well to tablet indomethacin and is presently asymptomatic and is being maintained on tablet indomethacin after 6 months of follow-up.

Pseudo-Bartter syndrome as the initial presentation of cystic fibrosis in children: an important diagnosis not to be missed.

Pseudo-Bartter syndrome (PBS) is characterised by hyponatraemic, hypochloraemic metabolic alkalosis that mimics Bartter syndrome, without renal tubular disease. We present a case of an infant with a positive cystic fibrosis (CF) newborn screening, hospitalised during the summer with dehydration, oliguria and apathy. Blood analysis revealed hypochloraemic metabolic alkalosis, hypokalaemia and hyponatraemia. Urine analysis showed leucocyturia with reduced sodium and chloride excretion fraction, and urinary culture was positive for Citrobacter koseri After antibiotherapy and intravenous rehydration with additional supplementation of sodium and chloride, the patient recovered completely. PBS is one of CF complications that is especially prevalent in infants and young children with increased sweating and/or other causes of additional loss of sodium and chloride. Clinical awareness of this syndrome and its strong clinical suspicion are extremely important for an early diagnosis and treatment of CF, particularly in countries where the universal screening of CF is not routinely performed.

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.

Successful antenatal treatment of MAGED2-related Bartter syndrome and review of treatment options and efficacy.

A new form of transient antenatal Bartter syndrome (aBS) was recently identified that is associated with the X-linked MAGED2 variant. Case reports demonstrate that this variant leads to severe polyhydramnios that may result in preterm birth or pregnancy loss. There is limited but promising evidence that amnioreductions may improve fetal outcomes in this rare condition. We report a woman with two affected pregnancies. In the first pregnancy, the patient was diagnosed with mild-to-moderate polyhydramnios in the second trimester that ultimately resulted in preterm labor and delivery at 25 weeks with fetal demise. Whole exome sequencing of the amniotic fluid sample resulted after the pregnancy loss and revealed a c.1337G>A MAGED2 variant that was considered diagnostically. The subsequent pregnancy was confirmed by chorionic villi sampling to also be affected by this variant. The pregnancy was managed with frequent ultrasounds and three amnioreductions that resulted in spontaneous vaginal delivery at 37 weeks and 6 days of a viable newborn with no evidence of overt electrolyte abnormalities suggesting complete resolution. A detailed review of the published cases of MAGED2-related transient aBS is provided. Our review focuses on individuals who received antenatal treatment. A total of 31 unique cases of MAGED2-related transient aBS were compiled. Amnioreduction was performed in 23 cases and in 18 cases no amnioreduction was performed. The average gestational age at delivery was significantly lower in cases without serial amnioreduction (28.7 vs. 30.71 weeks, p = 0.03). Neonatal mortality was seen in 5/18 cases without serial amnioreduction, and no mortality was observed in the cases with serial amnioreduction. In cases of second trimester severe polyhydramnios without identifiable cause, whole exome sequencing should be considered. Intensive ultrasound surveillance and serial amnioreduction is recommended for the management of MAGED2-related transient aBS.

Pattern of hereditary renal tubular disorders in Egyptian children.

BACKGROUND: Hereditary renal tubular disorders (HRTD) represent a group of genetic diseases characterized by disturbances in fluid, electrolyte, and acid-base homeostasis. There is a paucity of studies on pediatric HRTD in Egypt. In this study, we aimed to study the pattern, characteristics, and growth outcome of HRTD at an Egyptian medical center. METHODS: This study included children from one month to < 18-years of age with HRTD who were diagnosed and followed up at the Pediatric Nephrology Unit of Sohag University Hospital from January 2015 to December 2021. Data on patients` demographics, clinical features, growth profiles, and laboratory characteristics were collected. RESULTS: Fifty-eight children (57% males; 72% parental consanguinity; 60% positive family history) were diagnosed with seven HRTD types. The most commonly encountered disorders were distal renal tubular acidosis (distal renal tubular acidosis [RTA] 27 cases, 46.6%) and Bartter syndrome (16 cases 27.6%). Other identified disorders were Fanconi syndrome (6 cases with cystinosis), isolated proximal RTA (4 cases), nephrogenic diabetes insipidus (3 cases), and one case for each RTA type IV and Gitelman syndrome. The median age at diagnosis was 17 months with a variable diagnostic delay. The most common presenting features were failure to thrive (91.4%), developmental delay (79.3%), and dehydration episodes (72.4%). Most children showed marked improvement in growth parameters in response to appropriate management, except for cases with Fanconi syndrome. Last, only one case (with cystinosis) developed end-stage kidney disease. CONCLUSIONS: HRTD (most commonly distal RTA and Bartter syndrome) could be relatively common among Egyptian children, and the diagnosis seems challenging and often delayed.

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.

Genotypic variability in patients with clinical diagnosis of Bartter syndrome type 3.

Bartter syndrome (BS) is a salt-losing hereditary tubulopathy characterized by hypokalemic metabolic alkalosis with secondary hyperaldosteronism. Confirmatory molecular diagnosis may be difficult due to genetic heterogeneity and overlapping of clinical symptoms. The aim of our study was to describe the different molecular findings in patients with a clinical diagnosis of classic BS. We included 27 patients (26 families) with no identified pathogenic variants in CLCNKB. We used a customized Ion AmpliSeq Next-Generation Sequencing panel including 44 genes related to renal tubulopathies. We detected pathogenic or likely pathogenic variants in 12 patients (44%), reaching a conclusive genetic diagnosis. Variants in SLC12A3 were found in 6 (Gitelman syndrome). Median age at diagnosis was 14.6 years (range 0.1-31), with no history of prematurity or polyhydramnios. Serum magnesium level was low in 2 patients (33%) but urinary calcium excretion was normal or low in all, with no nephrocalcinosis. Variants in SLC12A1 were found in 3 (BS type 1); and in KCNJ1 in 1 (BS type 2). These patients had a history of polyhydramnios in 3 (75%), and the mean gestational age was 34.2 weeks (SD 1.7). The median age at diagnosis was 1.8 years (range 0.1-6). Chronic kidney disease and nephrocalcinosis were present in 1 (25%) and 3 (75%) patients, respectively. A variant in CLCN5 was found in one patient (Dent disease), and in NR3C2 in another patient (Geller syndrome). Genetic diagnosis of BS is heterogeneous as different tubulopathies can present with a similar clinical picture. The use of gene panels in these diseases becomes more efficient than the study gene by gene with Sanger sequencing.

HNF1B variant without hyperglycaemia as a cause of isolated profound hypomagnesaemia.

A young man presented unconscious with severe hyponatraemia, hypokalaemia, hypomagnesaemia and metabolic alkalosis. After 4 months of treatment in hospital, the hypomagnesaemia persisted. The patient had no signs of diabetes mellitus, and radiology showed no abnormalities of the kidneys, pancreas or genitourinary tract. A parenteral magnesium load demonstrated renal wasting with increased fractional urinary excretion of magnesium. Genetic tests for Gitelman as well as Bartter syndromes were negative. However, a wider genetic panel revealed that the patient was heterozygous for a deletion on chromosome band 17q12, encompassing the whole HNF1B gene.This case highlights the importance of considering pathogenic HNF1B variants in isolated profound hypomagnesaemia caused by renal wasting. Pathogenic HNF1B variants may partly mimic hypomagnesaemia found in Gitelman and Bartter syndromes and may be present without other features linked to HNF1B variants, including diabetes mellitus.