A case report and literature analysis of an infant with Batter syndrome caused by CLCNKA and CLCNKB gene mutation / 中国热带医学

@#Abstract: Bartter syndrome (BS) is a kind of inherited metabolic disease characterized by electrolyte and endocrine disorder, resulting from genetic gene mutation or deletion. Clinically, it manifests as vomiting, constipation, feeding difficulties, weight loss, growth retardation. The laboratory examination shows hypokalemia, metabolic alkalosis, hyperreninemia, aldosteronism, etc. As an autosomal recessive genetic disease, BS has an extremely low incidence rate, making diagnosis and treatment quite challenging. In recent years, with the progress of gene detection and other technologies, China has made great progress in the study of BS, more and more BS has been diagnosed accurately. According to known gene mutation types, it can be divided into type 1, type 2, type 3, type 4, type 5 and Gitelman syndrome, a total of 6 types, with type 4 further divided into type 4a and type 4b. At present, the most common type of children with BS in clinical practice is type 3, which is the classic type of BS. This paper reports a case of Bartter syndrome type 4b (BS4b). After two rounds of three-generation family gene sequencing, it was discovered that the infant had a combined mutation of both the CLCNKA and CLCNKB alleles, in addition to Alport syndrome, and both parents were carriers of this type of gene defect. The child was finally diagnosed as BS4b and Alport syndrome. This report, combined with the patient's clinical features, diagnosis and treatment process, as well as related literature analysis, aims to provide experience for understanding and diagnosis and treatment of this disease.

Variant analysis and genotype/phenotype association study in 42 Chinese patients with Bartter syndrome type 3 / 中华肾脏病杂志

Objective To analyze the variants of 42 Chinese patients with Bartter syndrome type 3 (BS3) and explore the characteristics of genotype and phenotype. Methods Forty-two genetically diagnosed patients from 40 Han and one Hui families were collected in the Affiliated Hospital of Qingdao University and the Affiliated Qingdao Municipal Hospital of Qingdao University during the period of June 2012 to October 2018. The second-generation sequencing and multiplex ligase probe-dependent amplification (MLPA) technique were used to analyze the CLCNKB gene variation and its characteristics in children with BS3. The clinical data were collected, and the therapeutic effect and growth improvement were observed and followed up. Thirty eight patients were divided into severe (n=26) and light (n=12) groups according to the severity of genetic variation. The clinical phenotypic characteristics of the two groups were compared. Results Thirty-six variants including 16 novel ones of CLCNKB gene were found. The whole gene deletion of CLCNKB gene was the most frequent mutation (40％), and the rate of large deletions was up to 55％. The most common symptoms included development retardation (38/42), polydipsia and polyuria (35/42), constipation (31/42) and vomiting (27/42). All patients presented with hypokalemia, hypochloremia and metabolic alkalosis. After the medicine treatment that based on indomethacin and potassium chloride, most patients could achieve obvious recovery of growth rate and restoration of hypokalemia. The severe group showed more severe metabolic alkalosis than the light group. Conclusions Thirty-six variants of CLCNKB gene have been found in this study, including 16 novel ones, which enrich the human gene mutation database (HGMD) and provide valuable references to diagnosis, treatment and the genetic counseling of Chinese population.

Gene analysis, treatment, and follow-up of sixteen Chinese patients with Bartter syndrome / 中华肾脏病杂志

Objective To analyze the mutations of causal genes in sixteen Chinese patients with suspicious Bartter syndrome,and follow up their treatment results.Methods Mutations were identified by the next generation sequencing and the multiplex ligation-dependent probe amplification (MLPA).Clinical and biochemical features at the first presentation as well as follow-up results were reviewed.Results 15 different CLCNKB gene mutations were identified in sixteen patients with BS,including 11 novel ones.A novel missense mutation and a novel small deletion were found from SLC12A1 gene.A novel gross deletion was found in CLCNKA gene.A recurrent missense mutation was identified from BSND gene.The whole gene deletion mutation of CLCNKB gene was the most frequent mutation (32％),and the rate of gross deletion was up to 50 percent in this group of Chinese patients.The most common clinical manifestations were development retardation (15/16),polydipsia and polyuria (15/16).All of the patients were detected with hypokalemia,hypochloremia and metabolic alkalosis.Indomethacin treatment had significant improvement to the stature and weight restoration.Conclusion The present study has found 19 mutations,including 14 novel ones,which enriches the human gene mutation database (HGMD) and provides valuable references to the genetic counseling and diagnosis of Chinese population.

A novel mutation of CLCNKB in a Korean patient of mixed phenotype of Bartter-Gitelman syndrome / 소아과

Bartter syndrome (BS) is an inherited renal tubular disorder characterized by low or normal blood pressure, hypokalemic metabolic alkalosis, and hyperreninemic hyperaldosteronism. Type III BS is caused by loss-of-function mutations in CLCNKB encoding basolateral ClC-Kb. The clinical phenotype of patients with CLCNKB mutations has been known to be highly variable, and cases that are difficult to categorize as type III BS or other hereditary tubulopathies, such as Gitelman syndrome, have been rarely reported. We report a case of a 10-year-old Korean boy with atypical clinical findings caused by a novel CLCNKB mutation. The boy showed intermittent muscle cramps with laboratory findings of hypokalemia, severe hypomagnesemia, and nephrocalcinosis. These findings were not fully compatible with those observed in cases of BS or Gitelman syndrome. The CLCNKB mutation analysis revealed a heterozygous c.139G>A transition in exon 13 [p.Gly(GGG)465Glu(GAG)]. This change is not a known mutation; however, the clinical findings and in silico prediction results indicated that it is the underlying cause of his presentation.

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.

Clinical features and genetic analysis of three patients with Gitelman syndrome / 中华内分泌代谢杂志

[Summary] The clinical data of 3 inpatients clinically diagnosed as Gitelman syndrome ( GS ) were collected. The genomic DNA was isolated from the peripheral blood and the primers were designed to amplify all the exons and flanking introns in the SLC12A3 and CLCNKB genes by PCR. Direct sequencing of PCR products in the two genes was performed in all patients. Three patients manifested with recurrent hypokalemia, hypomagnesemia, hypocalciuria, hypochloremic metabolic alkalosis, but normal blood pressure. Gene sequencing results showed that one novel mutation p. L891V was identified in SLC12A3 gene in case 2. Seven and 12 types of polymorphic loci in the CLCNKB gene were found in case 1 and case 3, respectively. However, mutations were not found in the SLC12A3 and CLCNKB gene.

Translational Read-Through of a Nonsense Mutation Causing Bartter Syndrome

Bartter syndrome (BS) is classified into 5 genotypes according to underlying mutant genes and BS III is caused by loss-of-function mutations in the CLCNKB gene encoding for basolateral ClC-Kb. BS III is the most common genotype in Korean patients with BS and W610X is the most common CLCNKB mutation in Korean BS III. In this study, we tested the hypothesis that the CLCNKB W610X mutation can be rescued in vitro using aminoglycoside antibiotics, which are known to induce translational read-through of a nonsense mutation. The CLCNKB cDNA was cloned into a eukaryotic expression vector and the W610X nonsense mutation was generated by site-directed mutagenesis. Cultured polarized MDCK cells were transfected with the vectors, and the read-through was induced using an aminoglycoside derivative, G418. Cellular expression of the target protein was monitored via immunohistochemistry. While cells transfected with the mutant CLCNKB failed to express ClC-Kb, G418 treatment of the cells induced the full-length protein expression, which was localized to the basolateral plasma membranes. It is demonstrated that the W610X mutation in CLCNKB can be a good candidate for trial of translational read-through induction as a therapeutic modality.

Analysis of CLCNKB gene mutation in a family with classic Bartter syndrome / 中华肾脏病杂志

Objective To investigate the mutations of CLCNKB gene in a family with classic Bartter syndrome. Methods Genetic DNA was extracted from peripheral blood leucocytes of family members.The coding exons and intron exon junctions of CLCNKB gene were amplyfied by PCR and sequenced directly.Fifty unrelated healthy subjects were selected to exclude the possibility of polymorphism. Results A heterozygous(missense)mutation(482T>G,L161R)was detected in the exon 4 of patients.The hetemzygous mutation(L161R)was found in the mother,while no mutation was found in the father of this family.L161R had not been reported and was a novel mutation when referring to literatures and human genomic database home and abroad.Conclusion A new CLCNKB gene mutation(L161R)is identified for the first time.

Study on CLCNKB gene mutation in a late-onset Chinese patient with classic Bartter syndrome / 中华肾脏病杂志

Objective To investigate the underlying mutation in a late-onset Chinese patient with classic Bartter syndrome. Methods The mutation analysis of CLCNKB gene was performed by the PCR direct sequencing. The patient's parents and siblings were studied as well. Fifty normal volunteers were analyzed as control group. Results The heterozygous deletion mutation cDNA 753delG and heterozygous missense mutation G433E were detected in the patient. Her father was found to carry heterozygous G433E and her mother to carry cDNA 753delG mutation respectively. Her brother carried heterozygous G433E and her sister was normal. Conclusions Two mutations of the CLCNKB gene in this Chinese patient with late-onset classic Bartter syndrome are identified. The cDNA 753delG mutation has not been reported previously.