Gitelman's syndrome: a pathophysiological and clinical update

First Diagnosis of Gitelman Syndrome During Pregnancy in an Adolescent Female: A Case Report

Gitelman syndrome (GS) is an inherited somatic recessive disorder characterized by hypokalemic metabolic alkalosis, accompanied by hypocalciuria and hypermagnesuria. It usually presents in late childhood or young adults with muscle weakness, tetany, or convulsions. Limited information is available in the literature regarding the proper management of this syndrome during pregnancy, as well as its effects on both the mother and the child. We herein present the case of a 16-year-old primigravida who was admitted to the emergency department with chief complaints of abdominal pain, weakness, and vomiting for the past three days during the 12th week of gestation. Routine blood investigations revealed hypokalemia and hypomagnesemia, and electrocardiography (ECG) showed ST-segment depressions. Further evaluation was performed due to persistent hypokalemia, and metabolic alkalosis, hypocalciuria, and hyperaldosteronism were found. Hence, a clinical diagnosis of GS took place. The pregnancy progressed smoothly without complications; potassium levels remained consistently below normal, requiring supplementation three times during pregnancy. Pregnant women with GS should be reported due to the rarity of cases, aiming to establish a standardized approach for monitoring and management.

Heart's Dangerous Symphony: Torsade De Pointes Unleashed by Gitelman Syndrome-Induced Hypomagnesemia

Gitelman syndrome (GS) is a rare autosomal recessive salt-losing renal tubular disorder associated with a mutation of SLC12A3 or CLCNKB genes which encodes the thiazide-sensitive sodium-chloride co-transporter (NCCT) in the distal renal tubule. It is inherited as an autosomal recessive disorder. Hypokalemia, metabolic alkalosis, hypomagnesemia, hypocalciuria, and renin-angiotensin-aldosterone system (RAAS) activation are characteristics of GS. GS is often misdiagnosed or underdiagnosed owing to its low incidence and lack of awareness. Its prevalence is estimated to be around 1-10 per 40,000 people. We report a case of cardiac arrest secondary to torsade de pointes (TdP) because of GS-induced hypomagnesemia. Our case highlights the importance of clinicians being aware of the potential electrolyte abnormalities and complications associated with GS, as it can lead to catastrophic consequences if not identified and corrected earlier.

Molecular complexity analysis of the diagnosis of Gitelman syndrome in China

Gitelman syndrome (GS) is an autosomal recessive renal tubal disease characterized by hypomagnesemia, hypokalemia, and hypocalciuria. The disease is caused by defects in the SLC12A3 gene, which encodes the thiazide diuretic-sensitive sodium chloride cotransporter (NCCT). In this study, a 20-year-old female patient with recurrent hypokalemia was tested for a hypokalemia-related panel using Next Generation Sequencing. Pedigree analysis was performed on her parents (non-consanguineous) and sister using Sanger sequencing. The results revealed that the patient carried compound heterozygous variants of the SLC12A3 gene: c.179C > T (p.T60M) and c.1001G > A (p.R334Q). Furthermore, her asymptomatic 6-year-old sister also carried both mutations. While the p.T60M mutation had been reported previously, the p.R334Q mutation was novel, and amino acid position 334 was identified as a mutation hotspot. Our findings provide an accurate molecular diagnosis that is essential for the diagnosis, counseling, and management of not only the symptomatic patient but also her asymptomatic sister. This study contributes to our understanding of the GS, which has a prevalence of approximately 1 in 40,000 and a heterozygous mutation carrier rate of 1% in Caucasians. Specifically, we observed a compound heterozygous mutation of the SLC12A3 gene in a 20-year-old female patient presenting with clinical symptoms consistent with GS.

A case of Gitelman syndrome with membranous nephropathy

Background

Gitelman syndrome (GS) is a rare autosomal recessive inherited salt-losing tubulopathy (SLT). Here, we report, for the first time, a case of GS overlapping nephrotic syndrome (NS) related to PLA2R-associated membranous nephropathy (MN).

Case presentation

We described a male patient had a 4-year history of recurrent fatigue. Serum biochemistry revealed hypokalemia with renal potassium wasting, hypomagnesemia, metabolic alkalosis, hyperreninemia, hypocalciuria, as well as nephrotic-range proteinuria, hypoalbuminemia, and elevated serum anti-phospholipase A2 receptor (PLA2R) antibody. Gene sequencing identified compound heterozygous mutations in SLC12A3 [c.536T > A(p.V179D) and c.1456G > A(p.D486N)]. The unusual association of SLTs and nephrotic-range glomerular proteinuria prompted us to perform a renal biopsy. Renal biopsy showed idiopathic MN. Due to the potential to activate the sodium-chloride co-transporter (NCC) and cause hyperkalemia, tacrolimus was selected to treat NS. Following treatment with potassium chloride, magnesium oxide, low-dose glucocorticoid combined with tacrolimus, the fatigue significantly improved, and concurrently hypokalemia, hypomagnesemia were corrected and NS was remitted.

Conclusions

Renal biopsy should be warranted for GS patients with moderate to nephrotic-range proteinuria. Tacrolimus was preferred to the management of GS patients with NS.

Three uncommon mutations of the SLC12A3 gene in gitelman syndrome: case reports and review of the literature

Background

Gitelman syndrome is a rare autosomal recessive salt-wasting tubulopathy characterized by low potassium and magnesium levels in the blood, decreased excretion of calcium in the urine, and metabolic alkalosis. It is commonly caused by an inactivating mutation in the SLC12A3 gene (16q13), which encodes a thiazide-sensitive sodium chloride cotransporter. Here, we present three cases with the same clinical and laboratory findings that showed different mutations in the SLC12A3 gene.

Case presentation

Three children, a 14-year-old boy, a 7-year-old girl, and an 11-year-old boy, were admitted to our hospital at different times with nausea, weakness, muscle cramps in hands, and failure to thrive complaints. Blood tests showed hypokalemia, hypomagnesemia and metabolic alkalosis. Patients were referred to Pediatric Nephrology Clinic and diagnosed with Gitelman syndrome. Genetic tests of three cases showed homozygous mutations of c.1928C > T, p.Pro643Leu, c.248G > A, p.Arg83Gln, and c.1919A > G, p.N640S in the SLC12A3 gene exists, respectively. Potassium chloride, magnesium replacements, and indomethacin were given for treatment to patients. During follow-up, patients' heights and weights were increased dramatically, and nausea complaints were over.

Conclusion

Different mutations in the SLC12A3 gene in Gitelman syndrome can be detected but clinical, and laboratory findings were generally similar. Treatment with potassium, magnesium supplements, and indomethacin showed significant improvements in symptoms.

High sodium chloride affects BMP-7 and 1α-hydroxylase levels through NCC and CLC-5 in NRK-52E cells

A diet high in sodium chloride (NaCl) can affect renal function damage and increase urinary calcium excretion, leading to bone loss. in renal tubules, Na-Cl co-transporter (NCC) and chloride channel 5 (CLC-5) are involved in regulating urinary calcium excretion. In addition, some cytokines, such as Bone morphogenetic protein 7 (BMP-7) and 1α-hydroxylase, are synthesized by renal tubules, which target on bone and play important roles on bone metabolism. However, the specific mechanisms between NaCl and these ion channels or cytokines still need investigations from many aspects. This study, in culture normal rat renal tubular epithelial NRK-52E cells, showed that high concentrations of NaCl significantly inhibited the cell viability and increased the cell apoptosis. High concentration of NaCl reduce bone mineral density (BMD), as demonstrated by the significantly increased mRNA and protein levels of NCC and osteopontin (OPN), but decreased the levels of CLC-5, BMP-7, and 1α-hydroxylase. In addition, we found that ovariectomized (OVX) rats on a high-salt diet for 12 weeks had altered levels of these indices in the renal cortices. Moreover, the BMD in fourth and fifth lumbar vertebra (LV4 and 5) and femurs were significantly decreased and bone microstructure was destroyed of these rats. We also demonstrated that high concentration of NaCl enhanced the inhibition of these cytokines which is beneficial to increase BMD, induced by modulating ion channels NCC and CLC-5. In conclusion, our results indicate that high concentration of NaCl reduce BMD by regulating ion channels NCC and CLC-5.

Gitelman syndrome and ectopic calcification in the retina and joints

Gitelman syndrome is a rare inherited renal tubular disorder with features that resemble thiazide use, including a hypokalemic metabolic alkalosis, hypomagnesemia, hypocalciuria and a low or normal blood pressure, hyperreninemia and hyperaldosteronism. Treatment is primarily correction of the potassium and magnesium levels. The diagnosis is confirmed with genetic testing but Gitelman syndrome is often not suspected. However, the association with ectopic calcification in the retina, blood vessels and chondrocalcinosis in the joints is a useful pointer to this diagnosis. Bilateral symmetrical whitish deposits of calcium pyrophosphate are visible superotemporally on ophthalmoscopy and retinal photography but are actually located beneath the retina in the sclerochoroid. Optical coherence tomography is even more sensitive for their detection. These deposits increase in size with time, but the rate of progression slows with long-term correction of the hypomagnesemia. Calcification may be complicated by atrophy of the overlying retina and visual loss. The deposits often correlate with ectopic calcification in the aorta and coronary and cerebral vessels. Chondrocalcinosis occurs in the large joints such as the knees. Ectopic calcification in Gitelman syndrome indicates the need for more aggressive management of Mg levels. Calcification is much less common in Bartter syndrome, which itself is rarer and associated less often with hypomagnesemia.

Review and Analysis of Two Gitelman Syndrome Pedigrees Complicated with Proteinuria or Hashimoto's Thyroiditis Caused by Compound Heterozygous SLC12A3 Mutations

Gitelman syndrome (GS) is an autosomal recessive inherited salt-losing renal tubular disease, which is caused by a pathogenic mutation of SLC12A3 encoding thiazide-sensitive Na-Cl cotransporter, which leads to disturbance of sodium and chlorine reabsorption in renal distal convoluted tubules, resulting in phenotypes such as hypovolemia, renin angiotensin aldosterone system (RAAS) activation, hypokalemia, and metabolic alkalosis. In this study, two GS families with proteinuria or Hashimoto's thyroiditis were analyzed for genetic-phenotypic association. Sanger sequencing revealed that two probands carried SLC12A3 compound heterozygous mutations, and proband A carried two pathogenic mutations: missense mutation Arg83Gln, splicing mutation, or frameshift mutation NC_000016.10:g.56872655_56872667 (gcggacatttttg>accgaaaatttt) in exon 8. Proband B carries two missense mutations: novel Asp839Val and Arg904Gln. Both probands manifested hypokalemia, hypomagnesemia, hypocalcinuria, metabolic alkalosis, and RAAS activation; in addition, the proband A exhibited decreased urinary chloride, phosphorus, and increased magnesium ions excretion, complicated with Hashimoto's Thyroiditis, while the proband B exhibited enhanced urine sodium excretion and proteinuria. The older sister of proband B with GS also had Hashimoto's thyroiditis. Electron microscopy revealed swelling and vacuolar degeneration of glomerular epithelial cells, diffuse proliferation of mesangial cells and matrix, accompanied by a small amount of low-density electron-dense deposition, and segmental fusion of epithelial cell foot processes in proband B. Light microscopy showed mild mesangial hyperplasia in the focal segment of the glomerulus, hyperplasia, and hypertrophy of juxtaglomerular apparatus cells, mild renal tubulointerstitial lesions, and one glomerular sclerosis. So, long-term hypokalemia of GS can cause kidney damage and may also be susceptible to thyroid disease.

Kidney stones and moderate proteinuria as the rare manifestations of Gitelman syndrome

Background

Gitelman syndrome (GS) is an autosomal recessive inherited salt-losing tubulopathy (SLT). Here, we describe, for the first time, a case of GS without Gitelman-like features and with concomitant kidney stones, cysts and diabetic nephropathy (DN).

Case presentation

We described a male patient had a 19-year history of recurrent fatigue. From childhood, he had polydipsia and polyuria, paroxysmal tetany and palpitation. Serum biochemistry revealed chronic hypokalemia, metabolic alkalosis, normomagnesemia, mildly elevated Cr. Concomitant 24 h urine collection showed inappropriate renal potassium wasting, borderline hypercalciuria, moderate proteinuria consisting of major glomerular. Ultrasound of urinary tract showed bilateral and multiple kidney stones and cysts. Whole exome sequencing (WES) identified compound heterozygous mutations of SLC12A3. The unusual association of SLTs and glomerular proteinuria prompted us to perform a renal biopsy. Renal pathology showed renal involvement consistent with GS and early stage of diabetic nephropathy (DN). After treatment with KCl, magnesium oxide, perindopril and acarbose, the patient had been cured. The fatigue didn’t relapse.

Conclusion

GS had high variability of phenotype, GS may have no Gitelman-like features, kidney stones are not the exclusion criteria of GS. Renal biopsy should be warranted for GS patients with moderate to massive glomerular proteinuria.

Calcium Transport in the Kidney and Disease Processes

Calcium is a key ion involved in cardiac and skeletal muscle contractility, nerve function, and skeletal structure. Global calcium balance is affected by parathyroid hormone and vitamin D, and calcium is shuttled between the extracellular space and the bone matrix compartment dynamically. The kidney plays an important role in whole-body calcium balance. Abnormalities in the kidney transport proteins alter the renal excretion of calcium. Various hormonal and regulatory pathways have evolved that regulate the renal handling of calcium to maintain the serum calcium within defined limits despite dynamic changes in dietary calcium intake. Dysregulation of renal calcium transport can occur pharmacologically, hormonally, and via genetic mutations in key proteins in various nephron segments resulting in several disease processes. This review focuses on the regulation transport of calcium in the nephron. Genetic diseases affecting the renal handling of calcium that can potentially lead to changes in the serum calcium concentration are reviewed.

Multiple neoplasia in a patient with Gitelman syndrome harboring germline monoallelic MUTYH mutation

Gitelman syndrome is a rare, recessively inherited disease characterized by chronic hypokalemia and hypomagnesemia as a result of defective electrolyte co-transport at the level of the distal convoluted tubule of the kidney. Here, we present the first report of a patient with Gitelman syndrome who developed multiple neoplasia including colorectal polyposis, synchronous colorectal cancers, recurrent breast fibroadenomata and a desmoid tumor. Whole-exome sequencing confirmed germline compound heterozygous mutations of c.179C > T and c.1326C > G in SLC12A3, and in addition, identified a monoallelic germline c.934-2A > G splice site mutation in MUTYH. In vitro, magnesium deficiency potentiated oxidative DNA damage in lymphoblastoid cell lines derived from the same patient. We postulate that monoallelic MUTYH mutations may manifest in the presence of cooperative non-genetic mechanisms, in this case possibly magnesium deficiency from Gitelman syndrome.

Gitelman syndrome in pregnancy: a case series

OBJECTIVE

To evaluate maternal and fetal outcomes in women with Gitelman syndrome (GS).

METHODS

Retrospective analysis of the clinical data of five patients with the clinical diagnosis of GS during pregnancy, who were admitted to Beijing Shijitan Hospital, Capital Medical University between 2013 and 2019, was conducted.

RESULTS

Five women with GS during pregnancy who finally gave birth to a total of eight newborns have been included. Three cases were primiparas and two cases were multiparas. Two cases were diagnosed before pregnancy and three cases were diagnosed in first or second trimester. The primary treatment was oral or intravenous electrolytes supplement. Three patients delivered through the vagina, and shoulder dystocia occurred in one patient. Two patients delivered by cesarean section, with one because of symptom of limb weakness during the course of labor and the other owing to gestational diabetes with fetal macrosomia. Postpartum hemorrhage and urinary retention were not reported in these cases. In perinatal period all the infants had good outcome. The children, aged between six months and five years, were healthy and well-developed during follow-up.

CONCLUSION

The maternal and perinatal outcome is usually favorable. We should pay attention to electrolyte examination in the first trimester in order to diagnose and manage the GS efficiently. Well-controlled patients with Gitelman syndrome can deliver through the vagina.

Early onset children's Gitelman syndrome with severe hypokalaemia: a case report

Background

Hypokalaemia is a common condition among paediatric patients, but severe hypokalaemia is rare and can be life-threatening if not treated properly. The causes of hypokalaemia are complex. Finding the root cause is the key.

Case presentation

This article reports on a 2-year-old boy with severe hypokalaemia who was diagnosed with pneumonia. The child’s lab findings were low blood potassium minimum level of 1.7 mmol/L, hypomagnesemia, and metabolic alkalosis. However, he was without the common features of hypokalaemia, such as respiratory paralysis, severe arrhythmia, weakness and decreased blood pressure. After recovering from pneumonia, his potassium levels did not return to normal. This outcome was suspected to be due to chronic renal loss of potassium. After undergoing second-generation gene sequencing tests, it was discovered he carried the SLC12A3 gene mutation with an Asp486Asn mutation site, which he had inherited from his mother. The final diagnosis was made, confirming the child suffered from Gitelman syndrome.

Conclusions

Genetic predisposition is an important cause of hypokalaemia in children. Children with unexplained persistent hypokalaemia should be examined for the possibility of Gitelman syndrome, which should be distinguished from Bartter syndrome. Genetic testing is the gold standard.

Identification of compound mutations of SLC12A3 gene in a Chinese pedigree with Gitelman syndrome exhibiting Bartter syndrome-liked phenotypes

Background

Gitelman syndrome is a rare salt-losing renal tubular disorder associated with mutation of SLC12A3 gene, which encodes the Na-Cl co-transporter (NCCT). Gitelman syndrome is characterized by hypokalemia, metabolic alkalosis, hypomagnesemia, hypocalciuria, and renin-angiotensin-aldosterone system (RAAS) activation. Different SLC12A3 variants may lead to phenotypic variability and severity.

Methods

In this study, we reported the clinical features and genetic analysis of a Chinese pedigree diagnosed with Gitelman syndrome.

Results

The proband exhibited hypokalaemia, hypomagnesemia, metabolic alkalosis, but hypercalciuria and kidney stone formation. The increased urinary calcium excretion made it confused to Bartter syndrome. The persistent renal potassium wasting resulted in renal tubular lesions, and might affect urinary calcium reabsorption and excretion. Genetic analysis revealed mutations of SLC12A3 gene with c.433C > T (p.Arg145Cys), c.1077C > G (p.Asn359Lys), and c.1666C > T (p.Pro556Ser). Potential alterations of structure and function of NCCT protein due to those genetic variations of SLC12A3 are predicted. Interestingly, one sibling of the proband carried the same mutant sites and exhibited similar clinical features with milder phenotypes of hypokalemia and hypomagnesemia, but hypocalciuria rather than hypercalciuria. Family members with at least one wild type copy of SLC12A3 had normal biochemistry. With administration of spironolactone, potassium chloride and magnesium supplement, the serum potassium and magnesium were maintained within normal ranges.

Conclusions

In this study, we identified compound mutations of SLC12A3 associated with varieties of clinical features. Further efforts are needed to investigate the diversity in clinical manifestations of Gitelman syndrome and its correlation with specific SLC12A3 mutations.

Gitelman syndrome caused by a novel hemiallelic missense mutation in SLC12A3 revealed by 16q12.2q21 microdeletion

Gitelman syndrome (GS) is caused by biallelic mutations in SLC12A3 as an autosomal recessive trait. A patient with a de novo 16q12.2q21 microdeletion showed clinical features of GS. SLC12A3 included in the deletion was analyzed, and a rare missense variant (c.1222A>C [p.N406H]) was identified as hemizygous. Consequently, GS was caused by the revealed SLC12A3 variant owing to chromosomal microdeletion.

The challenges of diagnosis and management of Gitelman syndrome

Gitelman syndrome is an inherited tubulopathy characterized by renal salt wasting from the distal convoluted tubule. Defects in the sodium chloride cotransporter (encoded by SLC12A3) underlie this autosomal recessive condition. This article focuses on the specific challenges of diagnosing and treating Gitelman syndrome, with use of an illustrative case report. Symptoms relate to decreased serum potassium and magnesium levels, which include muscle weakness, tetany, fatigue and palpitations. Sudden cardiac deaths have been reported. Making a diagnosis may be difficult given its rarity but is important. A knowledge of the serum and urine biochemical picture is vital to distinguish it from a broad differential diagnosis, and application of genetic testing can resolve difficult cases. There is a group of Gitelman syndrome heterozygous carriers that experience symptoms and electrolyte disturbance and these patients should be managed in a similar way, though here genetic investigations become key in securing a difficult diagnosis. Potassium and magnesium replacement is the cornerstone of treatment, though practically this can be hard for patients to manage and often does not fully relieve symptoms even when serum levels are normalized. Challenges arise due to the lack of randomized controlled trials focussing on treatment of this rare disease; hence, clinicians endorse strategies in line with correction of the underlying pathophysiology such as sodium loading or pharmacological treatments, which seem to help some patients. Focussed dietary advice and knowing the best tolerated preparations of potassium and magnesium medications are useful tools for the physician, as well as an awareness of the specific burdens that this patient group face in order to signpost appropriate support.

A case of Gitelman syndrome: our experience with a patient treated in clinical practice on a local island

Background: Gitelman syndrome (GS) is an autosomal recessive salt-losing renal tubulopathy resulting from mutations in the thiazide-sensitive Na-Cl cotransporter (NCC) gene. Notably, lack of awareness regarding GS and difficulty with prompt diagnosis are observed in clinical practice, particularly in rural settings.

Case presentation: We report a case of a 48-year-old man with GS who presented to a local clinic on a remote island. Occasional laboratory investigations incidentally revealed a reduced serum potassium level of 2.6 mmol/L. A careful medical interview revealed episodes of intermittent paralysis of the lower extremities and muscular weakness for >30 years. Subsequent laboratory investigations revealed hypomagnesemia, hypocalciuria, and hypokalemic metabolic alkalosis. Based on the patient’s history, clinical presentation, and laboratory investigations, we suspected GS. Genetic testing revealed a rare homozygous in-frame 18 base insertion in the NCC gene that might have resulted from the founder effect, consequent to his topographically isolated circumstances.

Conclusion: More case studies similar to our study need to be added to the literature to gain a deeper understanding of the functional consequences of this mutation and to establish optimal management strategies for this condition, particularly in rural clinical settings.

Characteristics and Follow-Up of 13 pedigrees with Gitelman syndrome

CONTEXT

Gitelman syndrome (GS) is clinically heterogeneous. The genotype and phenotype correlation has not been well established. Though the long-term prognosis is considered to be favorable, hypokalemia is difficult to cure.

OBJECTIVE

To analyze the clinical and genetic characteristics and treatment of all members of 13 GS pedigrees.

METHODS

Thirteen pedigrees (86 members, 17 GS patients) were enrolled. Symptoms and management, laboratory findings, and genotype-phenotype associations among all the members were analyzed.

RESULTS

The average ages at onset and diagnosis were 27.6 ± 10.2 years and 37.9 ± 11.6 years, respectively. Males were an average of 10 years younger and exhibited more profound hypokalemia than females. Eighteen mutations were detected. Two novel mutations (p.W939X, p.G212S) were predicted to be pathogenic by bioinformatic analysis. GS patients exhibited the lowest blood pressure, serum K⁺, Mg²⁺, and 24-h urinary Ca²⁺ levels. Although blood pressure, serum K⁺ and Mg²⁺ levels were normal in heterozygous carriers, 24-h urinary Na⁺ excretion was significantly increased. During follow-up, only 41.2% of patients reached a normal serum K⁺ level. Over 80% of patients achieved a normal Mg²⁺ level. Patients were taking 2-3 medications at higher doses than usual prescription to stabilize their K⁺ levels. Six patients were taking spironolactone simultaneously, but no significant elevation in the serum K⁺ level was observed.

CONCLUSION

The phenotypic variability of GS and therapeutic strategies deserve further research to improve GS diagnosis and prognosis. Even heterozygous carriers exhibited increased 24-h Na⁺ urine excretion, which may make them more susceptible to diuretic-induced hypokalemia.

Gitelman Syndrome: A Rare Cause of Seizure Disorder and a Systematic Review

Gitelman syndrome is one of the few inherited causes of metabolic alkalosis due to salt losing tubulopathy. It is caused by tubular defects at the level of distal convoluted tubules, mimicking a thiazide-like tumor. It usually presents in late childhood or in teenage as nonspecific weakness, fatigability, polyuria, and polydipsia but very rarely with seizures. It is classically associated with hypokalemia, hypomagnesemia, hypocalciuria, hyperreninemia, and hyperaldosteronism. However, less frequently, it can present with normal magnesium levels. It is even rarer to find normomagnesemic patients of GS who develop seizures as the main complication since hypomagnesemia is considered the principal etiology of abnormal foci of seizure-related brain activity in GS cases. Interestingly, patients with GS are oftentimes diagnosed during pregnancy when the classic electrolyte pattern consistent with GS is noticed. Our case presents GS with normal serum magnesium in a patient, with seizures being the main clinical presentation. We also did a comprehensive literature review of 122 reported cases to show the prevalence of normal magnesium in GS cases and an overview of clinical and biochemical variability in GS. We suggest that further studies and in-depth analysis are required to understand the pathophysiology of seizures in GS patients with both normal and low magnesium levels.

Two cases of successful pregnancy in patients with Gitelman's syndrome

Gitelman's syndrome (GS) is a distal convoluted tubule (DCT) defect clinically characterized by hypokalemic metabolic alkalosis. Pregnancy in women with GS often results in severe hypomagnesemia and hypokalemia. We report two cases of successful pregnancies, after previous fetal loss, in patients with GS managed with aggressive oral and intravenous electrolyte repletion. These cases illustrate increased potassium and magnesium requirements over the course of the pregnancies and are notable due to the high doses of electrolytes required. They also demonstrate the possibility of successful pregnancy outcomes with frequent laboratory monitoring and aggressive titration of electrolyte replacement either orally or intravenously to maintain appropriate serum levels necessary to provide a suitable environment for fetal development.

Gitelman syndrome in a South African family presenting with hypokalaemia and unusual food cravings

BACKGROUND

Gitelman syndrome (GS) is an autosomal recessive renal tubular disorder characterised by renal salt wasting with hypokalaemia, metabolic alkalosis, hypomagnesaemia and hypocalciuria. It is caused by mutations in SLC12A3 encoding the sodium-chloride cotransporter on the apical membrane of the distal convoluted tubule. We report a South African family with five affected individuals presenting with hypokalaemia and unusual food cravings.

METHODS

The affected individuals and two unaffected first degree relatives were enrolled into the study. Phenotypes were evaluated through history, physical examination and biochemical analysis of blood and urine. Mutation screening was performed by sequencing of SLC12A3, and determining the allele frequencies of the sequence variants found in this family in 117 ethnically matched controls.

RESULTS

The index patient, her sister, father and two aunts had a history of severe salt cravings, fatigue and tetanic episodes, leading to consumption of large quantities of salt and vinegar. All affected individuals demonstrated hypokalaemia with renal potassium wasting. Genetic analysis revealed that the pseudo-dominant pattern of inheritance was due to compound heterozygosity with two novel mutations: a S546G substitution in exon 13, and insertion of AGCCCC at c.1930 in exon 16. These variants were present in the five affected individuals, but only one variant each in the unaffected family members. Neither variant was found in any of the controls.

CONCLUSIONS

The diagnosis of GS was established in five members of a South African family through clinical assessment, biochemical analysis and mutation screening of the SLC12A3 gene, which identified two novel putative pathogenic mutations.

New SLC12A3 disease causative mutation of Gitelman’s syndrome

Gitelman’s syndrome (GS) is a salt-losing tubulopathy with an autosomal recessive inheritance caused by mutations of SLC12A3, which encodes for the thiazide-sensitive NaCl cotransporter. In this study we report a new mutation of SLC12A3 found in two brothers affected by GS. Hypokalemia, hypocalciuria and hyper-reninemia were present in both patients while hypomagnesemia was detected only in one. Both patients are compound heterozygotes carrying one well known GS associated mutation (c.2581 C > T) and a new one (c.283delC) in SLC12A3 gene. The new mutation results in a possible frame-shift with a premature stop-codon (pGln95ArgfsX19). The parents of the patients, heterozygous carriers of the mutations found in SLC12A3, have no disease associated phenotype. Therefore, the new mutation is causative of GS.

A novel homozygous mutation in the solute carrier family 12 member 3 gene in a Chinese family with Gitelman syndrome

Loss of function of mutated solute carrier family 12 member 3 (SLC12A3) gene is the most frequent etiology for Gitelman syndrome (GS), which is mainly manifested by hypokalemia, hypomagnesemia and hypocalciuria. We report the genetic characteristics of one suspicious Chinese GS pedigree by gene sequencing. Complete sequencing analysis of the SLC12A3 gene revealed that both the proband and his elder sister had a novel homozygous SLC12A3 mutation: c.2099T>C and p.Leu700Pro. Moreover, the SLC12A3 genes of his mother and daughter encoded the same mutated heterozygote. It was noted that in this pedigree, only the proband complained about recurrent episodes of bilateral lower limb weakness over 8 years, while his elder sister, mother and daughter did not present symptoms. The inconsistent clinical features of this pedigree implied that besides diverse phenotypes possibly originated from the same genotype, gender difference may also dominate the variant GS phenotypes. Further genetic and proteomic research are needed to investigate the precise mechanisms of GS, including the study of specific ethnicities.

Mutation profile and treatment of Gitelman syndrome in Chinese patients

BACKGROUND

Gitelman syndrome (GS) is a rare autosomal recessive disease caused by loss-of-function mutations in the SLC12A3 gene, and is characterized by hypokalemia and metabolic alkalosis. In this study, we aimed to study the genotype, phenotype, and treatment in 42 GS patients, the largest sample size so far in mainland China.

METHOD

We retrospectively studied the clinical data and genetic characteristics of 42 patients diagnosed with GS in Peking Union Medical College Hospital from 2012 to 2015. Therapeutic efficacy of spironolactone and potassium supplements was also studied retrospectively.

RESULTS

Eighty-one mutation alleles were found in 42 patients, and total of 52 distinctly different mutation alleles were identified, of which 15 were new mutation alleles. p.Asp486Asn was a hotspot in our series, with the allele frequency being 19.7 % (16/81), and was found in 13 patients (31.0 %). Treatment with spironolactone or potassium supplements alone significantly increased serum potassium concentration by 0.36 ± 0.37 and 0.45 ± 0.35 mmol/l, respectively (both P < 0.05), and combined therapy with spironolactone and potassium increased serum potassium concentration by 0.69 ± 0.64 mmol/l (P < 0.05).

CONCLUSIONS

18.5 % (15/81) mutation sites identified in 42 Chinese GS patients are novel. p.Asp486Asn mutation is a hotspot, which is different from the reports from other countries. Spironolactone could moderately elevate serum potassium level, and spironolactone in combination with potassium supplements tended to be more effective.

An Adult Case of Bartter Syndrome Type III Presenting with Proteinuria

Bartter syndrome (BS) I–IV is a rare autosomal recessive disorder affecting salt reabsorption in the thick ascending limb of the loop of Henle. This report highlights clinicopathological findings and genetic studies of classic BS in a 22-year-old female patient who presented with persistent mild proteinuria for 2 years. A renal biopsy demonstrated a mild to moderate increase in the mesangial cells and matrix of most glomeruli, along with marked juxtaglomerular cell hyperplasia. These findings suggested BS associated with mild IgA nephropathy. Focal tubular atrophy, interstitial fibrosis, and lymphocytic infiltration were also observed. A genetic study of the patient and her parents revealed a mutation of the CLCNKB genes. The patient was diagnosed with BS, type III. This case represents an atypical presentation of classic BS in an adult patient. Pathologic findings of renal biopsy combined with genetic analysis and clinicolaboratory findings are important in making an accurate diagnosis.

Mutations in SLC12A3 and CLCNKB and Their Correlation with Clinical Phenotype in Patients with Gitelman and Gitelman-like Syndrome

Gitelman's syndrome (GS) is caused by loss-of-function mutations in SLC12A3 and characterized by hypokalemic metabolic alkalosis, hypocalciuria, and hypomagnesemia. Long-term prognosis and the role of gene diagnosis in GS are still unclear. To investigate genotype-phenotype correlation in GS and Gitelman-like syndrome, we enrolled 34 patients who showed hypokalemic metabolic alkalosis without secondary causes. Mutation analysis of SLC12A3 and CLCNKB was performed. Thirty-one patients had mutations in SLC12A3, 5 patients in CLCNKB, and 2 patients in both genes. There was no significant difference between male and female in clinical manifestations at the time of presentation, except for early onset of symptoms in males and more profound hypokalemia in females. We identified 10 novel mutations in SLC12A3 and 4 in CLCNKB. Compared with those with CLCNKB mutations, patients with SLC12A3 mutations were characterized by more consistent hypocalciuria and hypomagnesemia. Patients with 2 mutant SLC12A3 alleles, compared with those with 1 mutant allele, did not have more severe clinical and laboratory findings except for lower plasma magnesium concentrations. Male and female patients did not differ in their requirement for electrolyte replacements. Two patients with concomitant SLC12A3 and CLCNKB mutations had early-onset severe symptoms and showed different response to treatment. Hypocalciuria and hypomagnesemia are useful markers in differentiation of GS and classical Bartter's syndrome. Gender, genotypes or the number of SLC12A3 mutant alleles cannot predict the severity of disease or response to treatment.

Acquired Gitelman Syndrome in an Anti-SSA Antibody-positive Patient with a SLC12A3 Heterozygous Mutation

A 36-year-old woman developed hypokalemic metabolic alkalosis after anti SS-A antibody was found to be positive. Diuretic loading test results were compatible with Gitelman syndrome (GS). The patient had a heterozygous mutation in SLC12A3, which encodes for thiazide-sensitive NaCl cotransporter (NCCT). While the mutation may be responsible for a latent hypofunction of NCCTs, the underlying anti-SSA antibody-associated autoimmunity induced the manifestation of its hypofunction. To the best of our knowledge, this is the first report to demonstrate that anti SS-A antibody-associated autoimmunity may induce GS in a patient with a SLC12A3 heterozygous mutation.

Identification of two novel mutations in SLC12A3 gene in two Chinese pedigrees with Gitelman syndrome and review of literature

OBJECTIVE

Gitelman syndrome (GS) is one of the most common causes of inherited hypokalaemia. As it was caused by mutations in the SLC12A3 gene, GS is a highly heterogeneous disease. Here, we aimed to investigate the clinical and genetic characteristics of two Chinese pedigrees and summarize the advance in GS genetics, diagnosis and management.

SUBJECTS AND METHODS

Two three-generation families with GS were identified and screened for mutations in the SLC12A3 gene. Genotype-phenotype correlations were analysed.

RESULTS

The two probands (A and B) were characterized by hypokalaemia, hypomagnesaemia and hypocalciuria without hypertension. Complete DNA sequencing of the SLC12A3 gene revealed two novel compound heterozygous mutations (c.179C>T and c.234delG; c.486-490delTACGGinsA and c.1925G>A), which are predicted to drastically affect normal protein structure. The female members of the pedigrees showed mild-to-no phenotype, although they carried the same mutations as the probands. Moreover, proband B presented with more severe symptoms than did proband A, which might be related to a lower serum magnesium level. During the 1-year follow-up, both probands showed satisfactory symptom improvement following the use of potassium and magnesium supplements.

CONCLUSION

Our findings strongly suggested that the two novel mutations in the SLC12A3 gene are the causative agents of GS, which may provide further insights into the function of this gene and help clinicians better understand this disorder.

Bartter and Gitelman syndromes: Spectrum of clinical manifestations caused by different mutations

Bartter and Gitelman syndromes (BS and GS) are inherited disorders resulting in defects in renal tubular handling of sodium, potassium and chloride. Previously considered as genotypic and phenotypic heterogeneous diseases, recent evidence suggests that they constitute a spectrum of disease caused by different genetic mutations with the molecular defects of chloride reabsorption originating at different sites of the nephron in each condition. Although they share some characteristic metabolic abnormalities such as hypokalemia, metabolic alkalosis, hyperplasia of the juxtaglomerular apparatus with hyperreninemia, hyperaldosteronism, the clinical and laboratory manifestations may not always allow distinction between them. Diuretics tests, measuring the changes in urinary fractional excretion of chloride from baseline after administration of either hydrochlorothiazide or furosemide show very little change (< 2.3%) in the fractional excretion of chloride from baseline in GS when compared with BS, except when BS is associated with KCNJ1 mutations where a good response to both diuretics exists. The diuretic test is not recommended for infants or young children with suspected BS because of a higher risk of volume depletion in such children. Clinical symptoms and biochemical markers of GS and classic form of BS (type III) may overlap and thus genetic analysis may specify the real cause of symptoms. However, although genetic analysis is available, its use remains limited because of limited availability, large gene dimensions, lack of hot-spot mutations, heavy workup time and costs involved. Furthermore, considerable overlap exists between the different genotypes and phenotypes. Although BS and GS usually have distinct presentations and are associated with specific gene mutations, there remains considerable overlap between their phenotypes and genotypes. Thus, they are better described as a spectrum of clinical manifestations caused by different gene mutations.

Regulation of blood pressure and renal function by NCC and ENaC: lessons from genetically engineered mice

The activity of the thiazide-sensitive Na(+)/Cl(-) cotransporter (NCC) and of the amiloride-sensitive epithelial Na(+) channel (ENaC) is pivotal for blood pressure regulation. NCC is responsible for Na(+) reabsorption in the distal convoluted tubule (DCT) of the nephron, while ENaC reabsorbs the filtered Na(+) in the late DCT and in the cortical collecting ducts (CCD) providing the final renal adjustment to Na(+) balance. Here, we aim to highlight the recent advances made using transgenic mouse models towards the understanding of the regulation of NCC and ENaC function relevant to the control of sodium balance and blood pressure. We thus like to pave the way for common mechanisms regulating these two sodium-transporting proteins and their potential implication in structural remodeling of the nephron segments and Na(+) and Cl(-) reabsorption.

Genetic and biological effects of sodium-chloride cotransporter (SLC12A3) in diabetic nephropathy

BACKGROUND/AIMS

Solute carrier family 12 member 3 (SLC12A3) encodes a sodium/chloride transporter in kidneys. Previous reports suggest that Arg913Gln polymorphism in this gene is associated with diabetic nephropathy (DN), but the data appear to be inconsistent. Up to now, there is no biological evidence concerning the effects of SLC12A3 in DN. In this study, we aim to evaluate the genetic effects of the SLC12A3 gene and its Arg913Gln polymorphism with genetic and functional analyses.

METHODS

We genotyped SLC12A3 genetic polymorphisms including Arg913Gln in 784 non-diabetes controls and 633 type 2 diabetes (T2D) subjects with or without DN in a Malaysian population and performed a meta-analysis of the present and previous studies. We further analyzed the role of slc12a3 in kidney development and progress of DN in zebrafish and db/db mice.

RESULTS

We found that SLC12A3 Arg913Gln polymorphism was associated with T2D (p = 0.028, OR = 0.772, 95% CI = 0.612-0.973) and DN (p = 0.038, OR = 0.547, 95% CI = 0.308-0.973) in the Malaysian cohort. The meta-analysis confirmed the protective effects of SLC12A3 913Gln allele in DN (Z-value = -1.992, p = 0.046, OR = 0.792). Furthermore, with knockdown of zebrafish ortholog, slc12a3 led to structural abnormality of kidney pronephric distal duct at 1-cell stage. Slc12a3 mRNA and protein expression levels were upregulated in kidneys of db/db mice from 6, 12, and 26 weeks at the age.

CONCLUSION

The present study provided the first biological and further genetic evidence that SLC12A3 has genetic susceptibility in the development of DN, while the minor 913Gln allele in this gene confers a protective effect in the disease.

Fanconi syndrome and severe polyuria: an uncommon clinicobiological presentation of a Gitelman syndrome

BACKGROUND

Gitelman syndrome is an autosomal recessive tubulopathy characterized by hypokalemia, hypomagnesemia, metabolic alkalosis and hypocalciuria. The majority of patients do not present with symptoms until late childhood or adulthood, and the symptoms are generally mild. We report here the first case of Gitelman syndrome presenting with the biological features of Fanconi syndrome and an early polyuria since the neonatal period. We discuss in this article the atypical electrolytes losses found in our patient, as well as the possible mechanisms of severe polyuria.

CASE PRESENTATION

A 6-year-old Caucasian girl was admitted via the Emergency department for vomiting, and initial laboratory investigations found hyponatremia, hypokalemia, metabolic acidosis with normal anion gap, hypophosphatemia, and hypouricemia. Urinalysis revealed Na, K, Ph and uric acid losses. Thus, the initial biological profile was in favor of a proximal tubular defect. However, etiological investigations were inconclusive and the patient was discharged with potassium chloride and phosphorus supplementation. Three weeks later, further laboratory analysis indicated persistent hypokalemia, a metabolic alkalosis, hypomagnesemia, and hypocalciuria. We therefore sequenced the SLC12A3 gene and found a compound heterozygosity for 2 known missense mutations.

CONCLUSIONS

Gitelman syndrome can have varying and sometimes atypical presentations, and should be suspected in case of hypokalemic tubular disorders that do not belong to any obvious syndromic entity. In this case, the proximal tubular dysfunction could be secondary to the severe hypokalemia. This report emphasizes the need for clinicians to repeat laboratory tests in undiagnosed tubular disorders, especially not during decompensation episodes.

Gitelman's syndrome associated with chondrocalcinosis: a case report

Gitelman's syndrome (GS) is a rare disease with autosomal recessive trait, characterized by hypokalemia, hypomagnesemia, metabolic alkalosis, hypocalciuria and hyperkinemic hyperaldosteronism. While muscle weakness, tetany, stomachache, nausea and fever are very common, it could sometimes be completely asymptomatic as is the case in our patient. It is generally benign, but some severe complications like growth retardation and, though rare, paralysis and cardiac arrest could also be seen. A 57-year-old male patient sent to our hospital for further examination because of hypokalemia was diagnosed with GS as a result of clinical and laboratory assessments. Potassium and magnesium replacement was started. We are presenting our case seeing that GS is not a syndrome to be overlooked as it bears a risk of severe complications, although it might be asymptomatic until advanced ages.