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

Antibiotic-induced Bartter-like syndrome: a systematic review

BACKGROUND

Bartter syndrome encompasses salt-losing tubulopathies characterized by hypokalaemia, hypochloremic metabolic alkalosis and hyperreninemic hyperaldosteronism with normal blood pressure and renal function. Acquired Bartter-like syndrome (ABLS) is commonly associated with diuretics and antibiotics such as aminoglycosides, colistin and amphotericin B. This review aims to understand the timing of Bartter syndrome onset after exposure to inciting drugs and explore its progression and management.

METHODS

A systematic review was conducted following PRISMA guidelines. Databases searched include PubMed, Embase, medRxiv and bioRxiv. Case reports, case series and review articles from 1986 to March 2022 were screened. Forty-three cases were included, consisting of five case series and the rest as case reports.

RESULTS

The most common antimicrobial associated with ABLS was gentamicin (41.8%), followed by colistin (32.5%). The most frequent symptoms were paraesthesias (27.9%) and carpopedal spasms (27.9%), while 32.5% of patients were asymptomatic. Laboratory findings showed hypokalaemia (100%), metabolic alkalosis (97.2%), hypocalcaemia (92.5%) and hypomagnesaemia (100%), with renal wasting of these electrolytes but normal serum creatinine. The median time for Bartter-like syndrome to appear post-drug exposure was 10 days (IQR 7-18 days), with resolution occurring within 14 days (IQR 7-31 days) after drug discontinuation. Symptoms resolved completely upon cessation of the offending agent.

CONCLUSIONS

ABLS, though rare, should be suspected in patients on antimicrobials presenting with salt-losing tubulopathy. Aminoglycosides are the most frequently implicated drugs. Discontinuation of the offending drug, along with fluid and electrolyte management, leads to complete recovery.

Gitelman syndrome presenting with lower limb paralysis: a case report

BACKGROUND

Gitelman syndrome is a rare autosomal recessive disorder that affects the distal convoluted tubules of the kidneys. It often manifests through various symptoms, including muscle weakness, paresthesia, fatigue, or paralysis. Owing to the scarcity of case reports regarding Gitelman syndrome in the Middle East and North Africa region, it is imperative to spread awareness about this syndrome for prompt diagnosis. Consequently, this could drastically decrease the rate of complications and help with its management and prognosis. This case report addresses the lack of awareness surrounding the syndrome. In addition to its unfamiliarity, the patient presented in this case exhibited hypokalemic periodic paralysis, which is a rare presentation of Gitelman syndrome. A 17-year-old Egyptian male patient presented to the emergency department complaining of progressive lower limb weakness during the previous week. The patient had recurrent, brief episodes of lower limb paralysis for more than 2 years. Clinical examination revealed severe lower limb weakness with a power of 0/5 bilaterally. There was no evidence of upper limb or respiratory muscle involvement. Further investigations revealed severe hypokalemia, hypomagnesemia, metabolic alkalosis, hypocalciuria, and hyperreninemia. A positive family history, along with the aforementioned laboratory results, supported the diagnosis of Gitelman syndrome. The patient was then transferred to the high-dependency care unit, where aggressive correction of hypokalemia and hypomagnesemia commenced. With the resolution of the lower limb weakness, the patient was discharged home in a stable condition.

CONCLUSION

Clinical history and biochemical findings helped in expediting the final diagnosis of Gitelman syndrome. With prompt electrolyte repletion, the patient regained full function and sensation in his lower limbs. Owing to the limited number of reported Gitelman syndrome cases within the Middle East and North Africa region, it is critical to increase exposure and knowledge of Gitelman syndrome.

Refractory Hypokalemia of Pregnancy: A Rare Case of Non-Aldosterone Mediated Hypokalemia

There is a wide differential for a patient presenting with hypokalemia and hypertension in pregnancy. Of these, Geller syndrome is a rare variant of mineralocorticoid receptor that leads to concomitant hypokalemia and gestational hypertension. Progesterone has been shown to have a high affinity for the mineralocorticoid receptor and thus antagonizes aldosterone functioning. However, in Geller syndrome, there is a mutation of the mineralocorticoid receptor with a resultant gain of function. Activation of the mutated receptor is characterized by hypertension and hypokalemia, which is exacerbated by the effect of progesterone and thereby presenting during pregnancy. Genetic testing can confirm the diagnosis of Geller syndrome. The management is supportive therapy and requires close monitoring of the patient and her fetus. Delivery of the fetus results in the resolution of both hypertension and hypokalemia. This report describes the case of a 25-year-old female patient with a history of alpha-1 antitrypsin deficiency who presented with symptomatic hypokalemia refractory to treatment in her third trimester.

ClC-Kb pore mutation disrupts glycosylation and triggers distal tubular remodeling

Mutations in the CLCNKB gene (1p36), encoding the basolateral chloride channel ClC-Kb, cause type 3 Bartter syndrome. We identified a family with a mixed Bartter/Gitelman phenotype and early-onset kidney failure and by employing a candidate gene approach, identified what we believe is a novel homozygous mutation (CLCNKB c.499G>T [p.Gly167Cys]) in exon 6 of CLCNKB in the index patient. We then validated these results with Sanger and whole-exome sequencing. Compared with wild-type ClC-Kb, the Gly167Cys mutant conducted less current and exhibited impaired complex N-linked glycosylation in vitro. We demonstrated that loss of Gly-167, rather than gain of a mutant Cys, impairs complex glycosylation, but that surface expression remains intact. Moreover, Asn-364 was necessary for channel function and complex glycosylation. Morphologic evaluation of human kidney biopsies revealed typical basolateral localization of mutant Gly167Cys ClC-Kb in cortical distal tubular epithelia. However, we detected attenuated expression of distal sodium transport proteins, changes in abundance of distal tubule segments, and hypokalemia-associated intracellular condensates from the index patient compared with control nephrectomy specimens. The present data establish what we believe are novel regulatory mechanisms of ClC-Kb activity and demonstrate nephron remodeling in humans, caused by mutant ClC-Kb, with implications for renal electrolyte handling, blood pressure control, and kidney disease.

Calcium Pyrophosphate Crystal Deposition: Insights to Risks Factors and Associated Conditions

PURPOSE OF THE REVIEW

This review provides an overview of medical conditions and risk factors associated with CPPD.

RECENT FINDINGS

Recent studies have indicated that CPPD patients may have a higher risk for systemic conditions such as cardiovascular diseases. Calcium pyrophosphate deposition disease (CPPD) is a common crystal arthropathy that primarily affects older adults, and, in most cases, the aetiology is idiopathic. Age is the most remarkable risk factor and due to the aging population, the prevalence of this condition is expected to increase. Strong evidence supports an association between CPPD and several metabolic and endocrine conditions, including hemochromatosis, hyperparathyroidism, hypomagnesemia, and hypophosphatasia. Additionally, there is growing evidence of an increased risk for cardiovascular diseases among CPPD patients, alongside potential links to rheumatic disorders, gender, medications, and joint trauma. Further research is needed to explore the underlying mechanisms linking CPPD to associated conditions and to develop targeted therapies with the aim of improving patient outcomes.

Bartter Syndrome With Recurrent Hypokalemic Periodic Paralysis: A Case Report

Hypokalemia is known to manifest as neurological weakness and cardiac rhythm disturbances. Severe hypokalemia can be life-threatening and needs prompt recognition and management. However, the workup for hypokalemia is equally essential to prevent future recurrences and complications. Bartter syndrome is one of the rare causes of hypokalemia, usually presenting early in childhood with growth retardation and failure to thrive. It is rare for a case to present in late adolescence. Here, we report a case who presented with recurrent hypokalemic paralysis and short stature in adolescence. We highlight the approach to hypokalemia and emphasize the need for early diagnosis to prevent potential complications.

An Unusual Presentation of Failure to Thrive in a Toddler: Bartter Syndrome

Bartter syndrome is a rare salt-wasting renal tubular disorder of autosomal-recessive inheritance. Antenatal Bartter syndrome (types I, II, and IV) manifests in infancy and has a more severe course compared to the classic Bartter syndrome (type III). This report details a unique instance of a male toddler, aged 18 months, who presented with failure to thrive, polydipsia, and polyuria. Blood gases revealed hypochloremic metabolic alkalosis with hyponatremia and hypokalemia. The diagnosis was confirmed by genetic testing, and the child was started on indomethacin and potassium supplementation. Despite being rare in children, this case report emphasizes the importance of looking beyond the usual in a child who presents with failure to thrive to prevent a delay in the diagnosis and treatment.

Renal Hypokalemia: An Endocrine Perspective

The majority of disorders that cause renal potassium wasting present with abnormalities in adrenal hormone secretion. While these findings frequently lead patients to seek endocrine evaluation, clinicians often struggle to accurately diagnose these conditions, delaying treatment and adversely impacting patient care. At the same time, growing insight into the genetic and molecular basis of these disorders continues to improve their diagnosis and management. In this review, we outline a practical integrated approach to the evaluation of renal hypokalemia syndromes that are seen in endocrine practice while highlighting recent advances in understanding of the genetics and pathophysiology behind them.

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.

A Comprehensive Review of Chloride Management in Critically Ill Patients

Chloride, often overshadowed in electrolyte management, emerges as a crucial player in the physiological intricacies of critically ill patients. This comprehensive review explores the multifaceted aspects of chloride, ranging from its significance in cellular homeostasis to the consequences of dysregulation in critically ill patients. The pathophysiology of hyperchloremia and hypochloremia is dissected, highlighting their intricate impact on acid-base balance, renal function, and cardiovascular stability. Clinical assessment strategies, including laboratory measurements and integration with other electrolytes, lay the foundation for targeted interventions. Consequences of dysregulated chloride levels underscore the need for meticulous management, leading to an exploration of emerging therapies and interventions. Fluid resuscitation protocols, the choice between crystalloids and colloids, the role of balanced solutions, and individualized patient approaches comprise the core strategies in chloride management. Practical considerations, such as monitoring and surveillance, overcoming implementation challenges, and embracing a multidisciplinary approach, are pivotal in translating theoretical knowledge into effective clinical practice. As we envision the future, potential impacts on critical care guidelines prompt reflections on integrating novel therapies, individualized approaches, and continuous monitoring practices. In conclusion, this review synthesizes current knowledge, addresses practical considerations, and envisions future directions in chloride management for critically ill patients. By embracing a holistic understanding, clinicians can navigate the complexities of chloride balance, optimize patient outcomes, and contribute to the evolving landscape of critical care medicine.

Long-Term Indomethacin Treatment in a Chinese Child with Gitelman Syndrome: Case Report and Literature Review on its Efficacy and Tolerance

BACKGROUND Gitelman syndrome (GS) is a rare inherited autosomal recessive salt-losing renal tubulopathy. Early-onset GS is difficult to differentiate from Bartter syndrome (BS). It has been reported in some cases that cyclooxygenase (COX) inhibitors, which pharmacologically reduce prostaglandin E2(PGE2) synthesis, are helpful for GS patients, especially in children, but the long-term therapeutic effect has not yet been revealed. CASE REPORT A 4-year-old boy was first brought to our hospital for the chief concern of short stature and growth retardation. Biochemical tests demonstrated severe hypokalemia, hyponatremia, and hypochloremic metabolic alkalosis. The patient's serum magnesium was normal. He was diagnosed with BS and treated with potassium supplementation and indomethacin and achieved stable serum potassium levels and slow catch-up growth. At 11.8 years of age, the patient showed hypomagnesemia and a genetic test confirmed that he had GS with compound heterozygous mutations in the SLC12A3 gene. At the age of 14.8 years, when indomethacin had been taken for nearly 10 years, the boy reported having chronic stomachache, while his renal function remained normal. After proton pump inhibitor and acid inhibitor therapy, the patient's symptoms were ameliorated, and he continued to take a low dose of indomethacin (37.5 mg/d divided tid) with good tolerance. CONCLUSIONS Early-onset GS in childhood can be initially misdiagnosed as BS, and gene detection can confirm the final diagnosis. COX inhibitors, such as indomethacin, might be tolerated by pediatric patients, and long-term therapy can improve the hypokalemia and growth retardation without significant adverse effects.

Adrenal Emergencies

The adrenal glands drive physiologic homeostasis, with dysregulation in any direction causing multisystem dysfunction. Adrenal excess states include hyperaldosteronism which manifests with refractory hypertension and electrolyte abnormalities including hypernatremia and hypokalemia. Paragangliomas including pheochromocytoma can cause multisystem end-organ dysfunction due to catecholaminergic storm, which require rapid blood pressure control with phentolamine and identification of lesions amenable to surgical resection. Adrenal insufficiency states in contrast can result in hypotension and decompensation refractory to vasopressor administration, requiring adrenal supplementation via hydrocortisone.

Two Brothers from Macedonia with Gitelman Syndrome

Gitelman syndrome (GS) is a rare renal tubulopathy with an autosomal recessive mode of inheritance, caused by biallelic pathogenic variants in the SLC12A3 gene. The clinical features may overlap with other disorders, such as Bartter syndrome type 3, HNF1B nephropathy or even mitochondrial disease, but can be distinguished by molecular genetic analysis. Here we report on two preschool brothers, who presented with a several months' history of episodes of carpopedal spasms and muscle aches. The biochemical analyses revealed hypokalemia and hypomagnesemia without metabolic alkalosis. A 24-h urine sample demonstrated hypocalciuria. The molecular analyses showed that both patients were heterozygous for 3 (likely) pathogenic variants in SLC12A3: c.1805_1806del; p. (Tyr602Cysfs*31), c.2660+1G>A and c.2944 A>T; p. (Ile982Phe). Analysis of the parents showed that the mother was heterozygous for the c.2944 A>T p.(Ile982Phe) variant, and the father carried the other 2 variants (c.1805_1806del and c.2660+1G>A). Herein we present two children in a family from N. Macedonia with clinical manifestations and electrolyte imbalances suggestive of GS. The results of the tubulopathy next generation sequencing (NGS) panel confirmed the diagnosis. The boys are treated with a high salt diet and oral potassium and magnesium supplements.

Bartter Syndrome-Related Variants Distribution: Brazilian Data and Its Comparison with Worldwide Cohorts

BACKGROUND

Genetic testing is recommended for accurate diagnosis of Bartter syndrome (BS) and serves as a basis for implementing specific target therapies. However, populations other than Europeans and North Americans are underrepresented in most databases and there are uncertainties in the genotype-phenotype correlation. We studied Brazilian BS patients, an admixed population with diverse ancestry.

METHODS

We evaluated the clinical and mutational profile of this cohort and performed a systematic review of BS mutations from worldwide cohorts.

RESULTS

Twenty-two patients were included; Gitelman syndrome was diagnosed in 2 siblings with antenatal BS and congenital chloride diarrhea in 1 girl. BS was confirmed in 19 patients: BS type 1 in 1 boy (antenatal BS); BS type 4a in 1 girl and BS type 4b in 1 girl, both of them with antenatal BS and neurosensorial deafness; BS type 3 (CLCNKB mutations): 16 cases. The deletion of the entire CLCNKB (1-20 del) was the most frequent variant. Patients carrying the 1-20 del presented earlier manifestations than those with other CLCNKB-mutations and the presence of homozygous 1-20 del was correlated with progressive chronic kidney disease. The prevalence of the 1-20 del in this BS Brazilian cohort was similar to that of Chinese cohorts and individuals of African and Middle Eastern descent from other cohorts.

CONCLUSION

This study expands the genetic spectrum of BS patients with different ethnics, reveals some genotype/phenotype correlations, compares the findings with other cohorts, and provides a systematic review of the literature on the distribution of BS-related variants worldwide.

Acquired autoimmune Bartter syndrome in a patient with primary hypothyroidism

We describe an unusual clinical presentation of autoimmune Bartter syndrome in a patient with primary hypothyroidism. A 65-year-old female patient was admitted with neuromuscular weakness associated with hypokalemia and metabolic alkalosis. She had a suboptimal response to potassium supplementation and potassium-sparing diuretic resulting in re-hospitalization with the same symptoms. A detailed serum and urinary biochemistry analysis in the absence of other causes of potassium wasting helped diagnose Bartter syndrome, a rare entity in adults. An autoimmune profile showed anti-Scl-70 antibody to be positive, although she did not develop other systemic features of the disease. Our patient responded to a steroid-based regimen potassium supplement, Indomethacin, and aldosterone antagonist with remarkable resolution of symptoms and correction of electrolyte derangement. We reviewed the literature to search for similar cases and included twenty-seven full-length publications on acquired and autoimmune causes of Bartter syndrome. Our case highlights the fact that hypokalemia with metabolic alkalosis in an adult patient should prompt clinicians to evaluate for common and uncommon conditions. While assessing for abnormal conditions, acquired Bartter syndrome should be considered if a patient has an underlying autoimmune, endocrine, or connective tissue disease.

The Impact of Gitelman Syndrome on Cardiovascular Disease: From Physiopathology to Clinical Management

Gitelman syndrome (GS), or congenital hypokalemic hypomagnesemia hypocalciuria with metabolic alkalosis, is a congenital inherited tubulopathy. This tubulopathy is associated with disorders of water-electrolyte homeostasis, such as metabolic alkalosis, hypokalemia, hyponatremia, hypomagnesemia and hypocalciuria. GS has an autosomal recessive inheritance. The loss-of-function mutation involves the gene that codifies for thiazide-sensitive sodium-chloride co-transporter located in the distal convoluted tubule. The physiopathology of the syndrome is characterized by activation of the renin-angiotensin-aldosterone system (RAAS) with a low plasmatic concentration of angiotensin-II. Despite hyper-activation of RAAS, average or low blood pressure is detected in association with low peripheral resistance and reduced response to vasopressors. Clinical findings are brief episodes of fatigue, syncope, vertigo, ataxia and blurred vision; sudden cardiac death might occur. This review aims to give insight into cardiovascular implications and management of GS.

A novel CLCNKB variant in a Chinese family with classic Bartter syndrome and prenatal genetic diagnosis

Background

Type III Bartter syndrome (BS), often known as classic Bartter syndrome is caused by variants in CLCNKB gene, which encoding the basolateral chloride channel protein ClC‐Kb, and is characterized by renal salt wasting, hypokalemia, metabolic alkalosis, increased renin, and aldosterone levels.

Methods

A 2‐year‐old boy presented severe malnutrition, severe metabolic alkalosis and severe hypokalemia and was clinically diagnosed with BS. The trio exome sequencing (ES) was performed to discover the genetic cause of this patient, followed by validation using Sanger sequencing and quantitative polymerase chain reaction subsequently.

Results

The genetic analysis indicated that this patient with a compound heterozygous variants of CLCNKB gene including a novel nonsense variant c.876 T > A and a whole‐gene deletion. The two variants were inherited from his parents, respectively. Subsequently, target sequencing of CLCNKB gene was performed for next pregnancy, and prenatal genetic diagnosis was provided for the family.

Conclusions

The results of current study identified the compound heterozygous variants in a patient with classic BS. The novel variant expands the spectrum of CLCNKB variants in BS. Our study also indicates that ES is an alternative tool to simultaneously detect single‐nucleotide variants and copy‐number variants.

Balancing Benefits and Risks of Indomethacin in the Management of Antenatal Bartter Syndrome: A Case Report

Background

Bartter syndrome, a very rare inherited renal tubular disorder, characterized by urinary salt wastage, hypokalemia, polyuria, and metabolic alkalosis, may manifest antenatally as severe isolated polyhydramnios. Indomethacin is known to reduce salt wastage and subsequent polyhydramnios during pregnancy; however, it reduces the Ductus Arteriosus diameter among other potential complications, such as inhibition of gastrointestinal perfusion and increasing the risk of renal toxicity.

Case

A 36-year-old multigravida presented with severe isolated polyhydramnios at 30 weeks of gestation. Based on a history of a previous pregnancy affected with Bartter syndrome, indomethacin was initiated. Amniotic fluid volume and Ductus Arteriosus diameter were monitored. As evidence lacks on optimal dose and duration of indomethacin, multiple-dose adjustments were made to reduce the amniotic fluid volume while maintaining normal Ductus Arteriosus diameter. Progressive polyhydramnios led to Cesarean section at 34+ weeks of gestation resulting in a healthy fetus diagnosed with Bartter syndrome in the early neonatal period.

Conclusion

We share our experience in the adjustment of the dose and duration of Indomethacin therapy in the treatment of severe polyhydramnios associated with antenatal Bartter syndrome. Amniotic fluid index, Ductus Arteriosus diameter, and umbilical artery doppler work together as key indicators to guide the success and safety of the therapy.

Geller Syndrome: A Rare Cause of Persistent Hypokalemia During Pregnancy

Geller syndrome is a rare disease and part of Mendelian forms of hypertension. This syndrome is caused by a mutation in the mineralocorticoid receptor with a resultant gain of function. It is characterized by hypertension and hypokalemia, which is exacerbated by the effect of progesterone and thereby presenting during pregnancy. Our patient is a 22-year-old female diagnosed with preeclampsia who presented with hypokalemia, refractory to treatment toward the end of her third trimester. The patient's hypokalemia resolved once she delivered her infant. Genetic testing is available, which can confirm the diagnosis of Geller syndrome. The management is supportive therapy and requires close monitoring of the patient and her fetus. Delivery of the fetus results in the resolution of both hypertension and hypokalemia. 

Clinical and Genetic Characterization of Patients with Bartter and Gitelman Syndrome

Bartter (BS) and Gitelman (GS) syndrome are autosomal recessive inherited tubulopathies, whose clinical diagnosis can be challenging, due to rarity and phenotypic overlap. Genotype-phenotype correlations have important implications in defining kidney and global outcomes. The aim of our study was to assess the diagnostic rate of whole-exome sequencing (WES) coupled with a bioinformatic analysis of copy number variations in a population of 63 patients with BS and GS from a single institution, and to explore genotype-phenotype correlations. We obtained a diagnostic yield of 86% (54/63 patients), allowing disease reclassification in about 14% of patients. Although some clinical and laboratory features were more commonly reported in patients with BS or GS, a significant overlap does exist, and age at onset, preterm birth, gestational age and nephro-calcinosis are frequently misleading. Finally, chronic kidney disease (CKD) occurs in about 30% of patients with BS or GS, suggesting that the long-term prognosis can be unfavorable. In our cohort the features associated with CKD were lower gestational age at birth and a molecular diagnosis of BS, especially BS type 1. The results of our study demonstrate that WES is useful in dealing with the phenotypic heterogeneity of these disorders, improving differential diagnosis and genotype-phenotype correlation.

Young Adults With Hereditary Tubular Diseases: Practical Aspects for Adult-Focused Colleagues

Recent advances in the management of kidney tubular diseases have resulted in a significant cohort of adolescents and young adults transitioning from pediatric- to adult-focused care. Most of the patients under adult-focused care have glomerular diseases, whereas rarer tubular diseases form a considerable proportion of pediatric patients. The purpose of this review is to highlight the clinical signs and symptoms of tubular disorders, as well as their diagnostic workup, including laboratory findings and imaging, during young adulthood. We will then discuss more common disorders such as cystinosis, cystinuria, distal kidney tubular acidosis, congenital nephrogenic diabetes insipidus, Dent disease, rickets, hypercalciuria, and syndromes such as Bartter, Fanconi, Gitelman, Liddle, and Lowe. This review is a practical guide on the diagnostic and therapeutic approach of tubular conditions affecting young adults who are transitioning to adult-focused care.

Early diagnosis of Gitelman syndrome in a young child: A case report

BACKGROUND

Gitelman syndrome (GS) is an autosomal recessive renal tubular disorder characterized by renal wasting hypokalemia, metabolic alkalosis, hypomagnesemia, and hypocalciuria. It is usually caused by mutations in the gene SLC12A3, which encodes the thiazide-sensitive Na-Cl cotransporter. GS is not usually diagnosed until late childhood or adulthood.

CASE SUMMARY

Here, we report the case of a one-year-old girl who was brought to the emergency department due to persistent vomiting for two days. On admission to our hospital, generalized weakness was observed, and laboratory investigations revealed severe hypokalemia (1.9 mmol/L). However, persistent hypokalemia was observed during outpatient follow-up. Suspicion of the GS phenotype was assessed via the patient’s clinical presentation, family history, and biochemical analysis of blood and urine. Further genetic analysis was performed for her and her family by exon-wide sequencing analysis of the gene SLC12A3. The genetic diagnosis of GS was established in the Taiwanese family with three affected individuals, two of whom were children (7 years/17 years) without obvious symptoms, with the youngest being only one year old (patient in our case).

CONCLUSION

We successfully demonstrated the early diagnosis of GS using family genetic analysis. Any instances of hypokalemia should not be neglected, as early detection of GS with suitable treatment can prevent patients from potentially life-threatening complications.

Successful living kidney donation from a patient with a Gitelman's syndrome

Living kidney donation from Gitelman's syndrome (GS) patients remains very rare. Long-term renal prognosis of donor and recipient patients remains unknown. We report a 67-year-old man with GS, harbouring a mutation of the SLC12A3 gene, who donated his kidney for transplant. Five years post-transplantation, his clinical condition and biochemical parameters remained stable with close monitoring and follow-up. Patients with non-complicated GS can be considered eligible to donate their kidney for transplant.

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.

Gitelman Syndrome in Pregnancy: A Clinical Challenge

PURPOSE

 Disease progress may be affected by pregnancy-related changes, and underlying conditions may also affekt pregnancy outcomes in women with Gitelman syndrome (GS). Case presentation A 35-year-old woman with GS (gravida 2 para 1) was referred to our hospital to start routine antenatal care follow-up at 6 weeks of gestation. At the age of 31, she had been diagnosed with GS after her first uneventful pregnancy. Upon early admission, her serum Mg+level was 0.51 mmol/L and her serum K+level 2.7 mmol/L with normal kidney function tests. She was already taking oral combined potassium citrate and potassium bicarbonate supplementation once a day before pregnancy. At the eighth gestational week, the medication was changed to an oral potassium color sachet of 1.5 gram per day until labor because of the insufficient dosage to maintain optimum potassium levels. She was also taking 365 milligrams of oral magnesium oxide twice a day before and during pregnancy. In the third trimester of the pregnancy, her serum Mg+level was 0.48 mmol/L and serum K+level 2.8 mmol/L. Because of the previous uterine surgery history, she underwent an elective cesarean operation at 39 weeks' gestation under spinal anesthesia and delivered a healthy 3090-gram female infant.

CONCLUSION

 Increased need for potassium and magnesium supplementation should be the critical considerations when managing pregnant patients with GS.

Diagnosis and outpatient management of Gitelman syndrome from the first trimester of pregnancy

A 32-year-old woman presented with an incidental finding of hypokalaemia on routine bloods at 9 weeks of a second pregnancy, on a background of lifelong salt craving. Her previous pregnancy was uncomplicated. She had no previous significant medical or family history. Venous blood gases showed a hypokalaemic, normochloraemic metabolic alkalosis. Urinary potassium was elevated. Escalating doses of oral supplementation of potassium, magnesium, sodium and potassium-sparing diuretics were required through the course of pregnancy, in response to regular electrolyte monitoring. These were later weaned and completely stopped post partum. Delivery was uneventful with no maternal or neonatal complications. Genetic testing performed post partum showed heterogenous mutation of SCL12A3 gene.

Mechanisms coupling sodium and magnesium reabsorption in the distal convoluted tubule of the kidney

Hypomagnesaemia is a common feature of renal Na+ wasting disorders such as Gitelman and EAST/SeSAME syndrome. These genetic defects specifically affect Na+ reabsorption in the distal convoluted tubule, where Mg2+ reabsorption is tightly regulated. Apical uptake via TRPM6 Mg2+ channels and basolateral Mg2+ extrusion via a putative Na+ -Mg2+ exchanger determines Mg2+ reabsorption in the distal convoluted tubule. However, the mechanisms that explain the high incidence of hypomagnesaemia in patients with Na+ wasting disorders of the distal convoluted tubule are largely unknown. In this review, we describe three potential mechanisms by which Mg2+ reabsorption in the distal convoluted tubule is linked to Na+ reabsorption. First, decreased activity of the thiazide-sensitive Na+ /Cl- cotransporter (NCC) results in shortening of the segment, reducing the Mg2+ reabsorption capacity. Second, the activity of TRPM6 and NCC are determined by common regulatory pathways. Secondary effects of NCC dysregulation such as hormonal imbalance, therefore, might disturb TRPM6 expression. Third, the basolateral membrane potential, maintained by the K+ permeability and Na+ -K+ -ATPase activity, provides the driving force for Na+ and Mg2+ extrusion. Depolarisation of the basolateral membrane potential in Na+ wasting disorders of the distal convoluted tubule may therefore lead to reduced activity of the putative Na+ -Mg2+ exchanger SLC41A1. Elucidating the interconnections between Mg2+ and Na+ transport in the distal convoluted tubule is hampered by the currently available models. Our analysis indicates that the coupling of Na+ and Mg2+ reabsorption may be multifactorial and that advanced experimental models are required to study the molecular mechanisms.

Gitelman syndrome caused by a rare homozygous mutation in the SLC12A3 gene: A case report

BACKGROUND

Gitelman syndrome (GS) is an unusual, autosomal recessive salt-losing tubulopathy characterized by hypokalemic metabolic alkalosis, hypomagnesemia and hypocalciuria. It is caused by mutations in the solute carrier family 12 member 3 (SLC12A3) gene resulting in disordered function of the thiazide-sensitive NaCl co-transporter. To date, many types of mutations in the SLC12A3 gene have been discovered that trigger different clinical manifestations. Therefore, gene sequencing should be considered before determining the course of treatment for GS patients.

CASE SUMMARY

A 55-year-old man was admitted to our department due to hand numbness and fatigue. Laboratory tests after admission showed hypokalemia, metabolic alkalosis and renal failure, all of which suggested a diagnosis of GS. Genome sequencing of DNA extracted from the patient’s peripheral blood showed a rare homozygous mutation in the SLC12A3 gene (NM_000339.2: chr16:56903671, Exon4, c.536T>A, p.Val179Asp). This study reports a rare homozygous mutation in SLC12A3 gene of a Chinese patient with GS.

CONCLUSION

Genetic studies may improve the diagnostic accuracy of Gitelman syndrome and improve genetic counseling for individuals and their families with these types of genetic disorders

AP-2β/KCTD1 Control Distal Nephron Differentiation and Protect against Renal Fibrosis

The developmental mechanisms that orchestrate differentiation of specific nephron segments are incompletely understood, and the factors that maintain their terminal differentiation after nephrogenesis remain largely unknown. Here, the transcription factor AP-2β is shown to be required for the differentiation of distal tubule precursors into early stage distal convoluted tubules (DCTs) during nephrogenesis. In contrast, its downstream target KCTD1 is essential for terminal differentiation of early stage DCTs into mature DCTs, and impairment of their terminal differentiation owing to lack of KCTD1 leads to a severe salt-losing tubulopathy. Moreover, sustained KCTD1 activity in the adult maintains mature DCTs in this terminally differentiated state and prevents renal fibrosis by repressing β-catenin activity, whereas KCTD1 deficiency leads to severe renal fibrosis. Thus, the AP-2β/KCTD1 axis links a developmental pathway in the nephron to the induction and maintenance of terminal differentiation of DCTs that actively prevents their de-differentiation in the adult and protects against renal fibrosis.

Splicing Characterization of CLCNKB Variants in Four Patients With Type III Bartter Syndrome

Objective

Type III Bartter syndrome (BS) is caused by loss-of-function mutations in the gene encoding basolateral chloride channel ClC-Kb (CLCNKB), and is characterized by hypokalemic metabolic alkalosis and hyperreninemic hyperaldosteronism. Here, we investigated the molecular defects in four Chinese children with clinical manifestations of Bartter syndrome.

Methods

The genomic DNA of the four patients was screened for gene variations using whole-exome sequencing (WES). The candidate variants were validated by direct Sanger sequencing. Quantitative PCR (qPCR) was subsequently performed to confirm the whole CLCNK gene deletion mutation. A minigene assay and reverse transcription PCR (RT-PCR) were performed to analyze the effect of splice variants in vitro.

Results

Our patients showed early onset age with hyponatremia, hypokalemia, hypochloremia, repeated vomiting and growth retardation, suggesting Bartter syndrome. Genetic analysis revealed that all patients carried compound heterozygous or homozygous truncating variants in the CLCNKB gene. In particular, we identified a novel nonsense variant c.239G > A (p.(Trp80*)), two splice site variants (c.1053-1 G > A and c.1228-2A > G), a whole gene deletion, and a novel synonymous variant c.228A > C (p.(Arg76Arg)) which located -2 bp from the 5′ splice donor site in exon 3. Furthermore, our in vitro minigene analysis revealed c.228A > C, c.1053-1G > A, and c.1228-2A > G cause the skipping of exon 3, exon 12, and exon 13, respectively.

Conclusion

Our results support that the whole CLCNKB gene deletion is the most common mutation in Chinese patients with type III BS, and truncating and whole gene deletion variants may account for a more severe phenotype of patients. We verified the pathogenic effect of three splicing variants (c.228A > C, c.1053-1G > A, and c.1228-2A > G) which disturbed the normal mRNA splicing, suggesting that splice variants play an important role in the molecular basis of type III BS, and careful molecular profiling of these patients will be essential for future effective personalized treatment options.

Loss of sodium chloride co-transporter impairs the outgrowth of the renal distal convoluted tubule during renal development

Background

Loss-of-function mutations in the sodium chloride (NaCl) co-transporter (NCC) of the renal distal convoluted tubule (DCT) cause Gitelman syndrome with hypokalemic alkalosis, hypomagnesemia and hypocalciuria. Since Gitelman patients are usually diagnosed around adolescence, we tested the idea that a progressive regression of the DCT explains the late clinical onset of the syndrome.

Methods

NCC wild-type and knockout (ko) mice were studied at Days 1, 4 and 10 and 6 weeks after birth using blood plasma analysis and morphological and biochemical methods.

Results

Plasma aldosterone levels and renal renin messenger RNA expression were elevated in NCC ko mice during the first days of life. In contrast, plasma ion levels did not differ between genotypes at age 10 days, but a significant hypomagnesemia was observed in NCC ko mice at 6 weeks. Immunofluorescent detection of parvalbumin (an early DCT marker) revealed that the fractional cortical volume of the early DCT is similar for mice of both genotypes at Day 4, but is significantly lower at Day 10 and is almost zero at 6 weeks in NCC ko mice. The DCT atrophy correlates with a marked reduction in the abundance of the DCT-specific Mg2+ channel TRPM6 (transient receptor potential cation channel subfamily M member 6) and an increased proteolytic activation of the epithelial Na+ channel (ENaC).

Conclusion

After an initial outgrowth, DCT development lags behind in NCC ko mice. The impaired DCT development associates at Day 1 and Day 10 with elevated renal renin and plasma aldosterone levels and activation of ENaC, respectively, suggesting that Gitelman syndrome might be present much earlier in life than is usually expected. Despite an early downregulation of TRPM6, hypomagnesemia is a rather late symptom.

Magnesium: The Forgotten Electrolyte-A Review on Hypomagnesemia

Magnesium is the fourth most abundant cation in the body and the second most abundant intracellular cation. It plays an important role in different organ systems at the cellular and enzymatic levels. Despite its importance, it still has not received the needed attention either in the medical literature or in clinical practice in comparison to other electrolytes like sodium, potassium, and calcium. Hypomagnesemia can lead to many clinical manifestations with some being life-threatening. The reported incidence is less likely than expected in the general population. We present a comprehensive review of different aspects of magnesium physiology and hypomagnesemia which can help clinicians in understanding, identifying, and treating this disorder.

The outcome of two pregnancies in a patient with Gitelman syndrome: case report and review of the literature

We report a case of a 30-year-old woman who was first found to have a persistently low serum potassium level at 26 years of age during her first pregnancy. Genetic test of SLC12A3 confirmed Gitelman syndrome. The patient remained asymptomatic and had two deliveries following spontaneous labor. The first neonate died of heart failure due to cardiac abnormalities. The obstetric and neonatal outcome of the second pregnancy was good.

Mimicry and well known genetic friends: molecular diagnosis in an Iranian cohort of suspected Bartter syndrome and proposition of an algorithm for clinical differential diagnosis

BACKGROUND

Bartter Syndrome is a rare, genetically heterogeneous, mainly autosomal recessively inherited condition characterized by hypochloremic hypokalemic metabolic alkalosis. Mutations in several genes encoding for ion channels localizing to the renal tubules including SLC12A1, KCNJ1, BSND, CLCNKA, CLCNKB, MAGED2 and CASR have been identified as underlying molecular cause. No genetically defined cases have been described in the Iranian population to date. Like for other rare genetic disorders, implementation of Next Generation Sequencing (NGS) technologies has greatly facilitated genetic diagnostics and counseling over the last years. In this study, we describe the clinical, biochemical and genetic characteristics of patients from 15 Iranian families with a clinical diagnosis of Bartter Syndrome.

RESULTS

Age range of patients included in this study was 3 months to 6 years and all patients showed hypokalemic metabolic alkalosis. 3 patients additionally displayed hypercalciuria, with evidence of nephrocalcinosis in one case. Screening by Whole Exome Sequencing (WES) and long range PCR revealed that 12/17 patients (70%) had a deletion of the entire CLCNKB gene that was previously identified as the most common cause of Bartter Syndrome in other populations. 4/17 individuals (approximately 25% of cases) were found to suffer in fact from pseudo-Bartter syndrome resulting from congenital chloride diarrhea due to a novel homozygous mutation in the SLC26A3 gene, Pendred syndrome due to a known homozygous mutation in SLC26A4, Cystic Fibrosis (CF) due to a novel mutation in CFTR and apparent mineralocorticoid excess syndrome due to a novel homozygous loss of function mutation in HSD11B2 gene. 1 case (5%) remained unsolved.

CONCLUSIONS

Our findings demonstrate deletion of CLCNKB is the most common cause of Bartter syndrome in Iranian patients and we show that age of onset of clinical symptoms as well as clinical features amongst those patients are variable. Further, using WES we were able to prove that nearly 1/4 patients in fact suffered from Pseudo-Bartter Syndrome, reversing the initial clinical diagnosis with important impact on the subsequent treatment and clinical follow up pathway. Finally, we propose an algorithm for clinical differential diagnosis of Bartter Syndrome.

Bartter Syndrome and Gitelman Syndrome

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

Bartter syndrome: causes, diagnosis, and treatment

Bartter syndrome is an inherited renal tubular disorder caused by a defective salt reabsorption in the thick ascending limb of loop of Henle, resulting in salt wasting, hypokalemia, and metabolic alkalosis. Mutations of several genes encoding the transporters and channels involved in salt reabsorption in the thick ascending limb cause different types of Bartter syndrome. A poor phenotype-genotype relationship due to the interaction with other cotransporters and different degrees of compensation through alternative pathways is currently reported. However, phenotypic identification still remains the first step to guide the suspicion of Bartter syndrome. Given the rarity of the syndrome, and the lack of genetic characterization in most cases, limited clinical evidence for treatment is available and the therapy is based mainly on the comprehension of renal physiology and relies on the physician's personal experiences. A better understanding of the mutated channels and transporters could possibly generate targets for specific treatment in the future, also encompassing drugs aiming to correct deficiencies in folding or plasma membrane expression of the mutated proteins.

Gitelman's Syndrome: characterization of a novel c.1181G>A point mutation and functional classification of the known mutations

We have investigated the mechanisms by which a novel missense point mutation (c.1181G>A) found in two sisters causes Gitelman's syndrome by impairing the sodium chloride co-transporter (NCC, encoded by SLC12A3 gene) function. The cDNA and in vitro transcribed mRNA of either wild-type or mutated SLC12A3 were transfected into HEK293 cells and injected into Xenopus laevis oocytes, respectively. The expression, maturation, trafficking, and function of the mutated and wild-type NCC were assessed by Western blotting, immunohistochemistry and ²²Na⁺ uptake studies. By immunoblotting of lysates from HEK293 cells and oocytes expressing wild-type NCC, two NCC-related bands of approximately 130 kDa and 115 kDa, corresponding to fully and core-glycosylated NCC, respectively, were identified. In contrast, the mutant NCC only showed a single band of approximately 115 kDa, indicating impaired maturation of the protein. Moreover, oocytes injected with wild-type NCC showed thiazide-sensitive ²²Na⁺ uptake, which was absent in those injected with the mutant NCC. The novel mutation was discussed in the context of the functionally characterized NCC mutations causing Gitelman's syndrome, which fit into five classes. In conclusion, the functional characterization of this novel Gly394Asp NCC and its localization on the NCC structure, alongside that of previously known mutations causing Gitelman's syndrome, may provide novel information on the function of the different domains of the human NCC.

Bartter Syndrome Type 3: Phenotype-Genotype Correlation and Favorable Response to Ibuprofen

Objective: To investigate the phenotype-genotype correlation in different genetic kinds of Bartter syndrome type 3 in children. Methods: Clinical and genetic data of 2 patients with different mutations in Bartter syndrome type 3 was analyzed while the prognosis was compared after a 6-year follow-up or 2-year follow-up, respectively. Results: Bartter syndrome is a kind of autosomal recessive inherited renal disorder. The manifestation and prognosis of Bartter syndrome change with mutation types, and severe mutation were often accompanied with unfavorable prognosis. Comprehensive therapy with ibuprofen, antisterone, captopril, and potassium have remarkable effect, while ibuprofen may improve growth retardation partly. Conclusion: Bartter syndrome should be considered when children have unreasonable continuous electrolyte disturbance, metabolic alkalosis and growth retardation.As a genetic disease, its clinical features depend on the mutation type. It can be ameliorated by electrolyte supplementation, prostaglandin synthetase inhibitors, angiotensin-converting enzyme inhibitors and potassium-sparing diuretic. Considering the following electrolyte disturbances, infections, growth retardation, kidney failure and even death, Bartter syndrome need lifelong treatment, early diagnosis and treatment is the most important.

Increased urinary prostaglandin E2 metabolite: A potential therapeutic target of Gitelman syndrome

BACKGROUND

Gitelman syndrome (GS), an inherited autosomal recessive salt-losing renal tubulopathy caused by mutations in SLC12A3 gene, has been associated with normal prostaglandin E2 (PGE2) levels since 1995 by a study involving 11 clinically diagnosed patients. However, it is difficult to explain why cyclooxygenase-2 (COX2) inhibitors, which pharmacologically reduce PGE2 synthesis, are helpful to patients with GS, and few studies performed in the last 20 years have measured PGE2 levels. The relationships between the clinical manifestations and PGE2 levels were never thoroughly analyzed.

METHODS

This study involved 39 GS patients diagnosed by SLC12A3 gene sequencing. Plasma and 24-h urine samples as well as the clinical data were collected at admission. PGE2 and PGEM levels were detected in plasma and urine samples by enzyme immunoassays. The in vivo function of the sodium-chloride co-transporter (NCC) in GS patients was evaluated using a modified thiazide test. The association among PGE2 levels, clinical manifestations and the function of NCC in GS patients were analyzed.

RESULTS

Significantly higher levels of urinary and plasma PGEM were observed in GS patients than in the healthy volunteers. Higher urinary PGEM levels indicated more severe clinical manifestations and NCC dysfunction estimated by the increase of Cl- clearance. A higher PGEM level was found in male GS patients, who showed earlier onset age and more severe hypokalemia, hypochloremia and metabolic alkalosis than female GS patients. No relationship between renin angiotensin aldosterone system activation and PGEM level was observed.

CONCLUSIONS

Higher urinary PGEM levels indicated more severe clinical manifestations and NCC dysfunction in GS patients. COX2 inhibition might be a potential therapeutic target in GS patients with elevated PGEM levels.

Rare Renal Diseases Can Be Used as Tools to Investigate Common Kidney Disorders

BACKGROUND

The prevention and slowing of chronic kidney disease still represent major challenges in nephrology. To this end, a major contribution may come from the extensive knowledge on the molecular pathways involved in the pathogenesis of rare kidney diseases, since it is now possible to shed light on several aspects of these pathologies thanks to the introduction of new technologies, including next-generation sequencing.

SUMMARY

In steroid-resistant nephrotic patients, a genetic background has been demonstrated in both children and adults; individualized mutations have been correlated with glomerular filtration barrier alterations. In addition, studies on genetic tubulopathies expressing hypertensive phenotypes can provide useful information for a correct diagnostic and therapeutic approach in patients with essential hypertension and a poor responsiveness to therapy.

KEY MESSAGE

This review deals with the pathogenesis of rare glomerular diseases and tubulopathies associated with hypertension, highlighting the importance of the study of rare diseases to better understand the molecular basis of more common and complex disorders leading to end-stage renal disease.

Is this a seizure?

We describe a case of a 65-year-old woman admitted to the hospital for suspected of epileptic crisis. She was affected by diabetes and hiatal hernia for which she was taking Proton Pump Inhibitors (PPI_s) for about 8 years. She showed hypocalcaemia, hypomagnesaemia, hyperparathyroidism and severe hypovitaminosis D. We exclude malabsorption and magnesium loss. After restored vitamin D levels, stopped use of PPI, start calcium and magnesium supplementation normal values of the ions were restored. This case underlies the importance of evaluate magnesium routinely, other than calcium and vitamin D, and use PPI more carefully.

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.

[Gene mutation analysis and prenatal diagnosis of a family with Bartter syndrome]

OBJECTIVE

To investigate the mutation of related genes and prenatal diagnosis of a family with Bartter syndrome (BS).

METHODS

The high-throughput capture sequencing technique and PCR-Sanger sequencing were used to detect pathogenic genes in the proband of this family and analyze the whole family at the genomic level. After the genetic cause was clarified, the amniotic fluid was collected from the proband's mother who was pregnant for 5 months for prenatal diagnosis.

RESULTS

The proband carried compound heterozygous mutations of c.88C>T(p.Arg30*) and c.968+2T>A in the CLCNKB gene; c.88C>T(p.Arg30*) had been reported as a pathogenic mutation, and c.968+2T>A was a new mutation. Pedigree analysis showed that the two mutations were inherited from the mother and father, respectively. Prenatal diagnosis showed that the fetus did not inherit the mutations from parents and had no mutations at the two loci. The follow-up visit confirmed that the infant was in a healthy state, which proved the accuracy of genetic diagnosis and prenatal diagnosis.

CONCLUSIONS

The compound heterozygous mutations c.88C>T(p.Arg30*) and c.968+2T>A in the CLCNKB gene are the cause of BS in the proband, and prenatal diagnosis can prevent the risk of recurrence of BS in this family.