1/28. Identification of a novel R642C mutation in Na/Cl cotransporter with Gitelman's syndrome.Gitelman's syndrome, a variant of Bartter's syndrome, is an inherited disorder characterized by hypokalemic metabolic alkalosis, hypomagnesemia, and hypocalciuria, and these abnormalities have recently been linked to the thiazide-sensitive Na/Cl cotransporter (TSC) gene. We evaluated three unrelated patients affected with this syndrome whose diagnosis was made based on clinical and biochemical features. The data of clearance studies in these patients were compatible with Gitelman's syndrome. We then investigated possible mutations of the TSC gene. In one patient whose parents are consanguineous, we identified a novel missense mutation in the TSC gene, which causes alteration of arginine to cysteine at codon 642 (R642C mutation) located in the cytoplasmic tail of the product. This mutation results in the loss of an MspI site in exon 15 of the TSC gene. MspI digestion analysis of genomic dna fragments from the family was consistent with the autosomal recessive inheritance of the disorder, and presence of this mutation correlated with the clinical manifestations. Such mutation was not detected in 47 normal healthy subjects. In the second patient, we found another missense mutation in one allele of the TSC gene, which results in alteration of arginine to glutamine at codon 955. In the third patient, no mutation causing amino acid substitution was found in the TSC gene. These results indicate that the R642C mutation in TSC is critically important for impairment of this cotransporter function and also suggest the necessity of further investigations in the genetic background of Gitelman's syndrome.- - - - - - - - - - ranking = 1keywords = dent (Clic here for more details about this article) |
2/28. Bartter's syndrome in pregnancy: a case report and review.Bartter's syndrome is a rare renal tubular disorder, involving juxtaglomerular cells hyperplasia, characterized by normotensive hyper-reninism and secondary hyperaldosteronism, marked renal loss of potassium and profound hypokalaemia. Both clinical and biochemical features are heterogeneous, ranging from the incidental finding in an asymptomatic patient to marked clinical features of hypokalaemia. Inheritance is likely to be an autosomal recessive. We present a case of Bartter's syndrome complicating pregnancy in a Chinese woman. We documented an increasing demand for potassium supplement during pregnancy which stabilized by mid-trimester. The absence of pregnancy complications such as polyhydramnios indicated that the fetus was unlikely to be affected by the condition.- - - - - - - - - - ranking = 0.2keywords = dent (Clic here for more details about this article) |
3/28. Phenotypic variability in bartter syndrome type I.Limited phenotypic variability has been reported in patients with bartter syndrome type I, with mutations in the Na-K-2Cl cotransporter gene (BSC). The diagnosis of this hereditary renal tubular disorder is usually made in the antenatal-neonatal period, due to the presence of polyhydramnios, premature delivery, hypokalemia, metabolic alkalosis, hypercalciuria, and nephrocalcinosis. Among nine children with hypercalciuria and nephrocalcinosis, we identified new mutations consistent with a loss of function of the mutant allele of the BSC gene in five. Three of the five cases with BSC gene mutations were unusual due to the absence of hypokalemia and metabolic alkalosis in the first years of life. The diagnosis of incomplete distal renal tubular acidosis was considered before molecular evaluation. Three additional patients with hypokalemia and hypercalciuria, but without nephrocalcinosis in the first two and with metabolic acidosis instead of alkalosis in the third, were studied. Two demonstrated the same missense mutation A555T in the BSC gene as one patient of the previous group, suggesting a single common ancestor. The third patient presented with severe hypernatremia and hyperchloremia for about 2 months, and a diagnosis of nephrogenic diabetes insipidus was hypothesized until the diagnosis of bartter syndrome type I was established by molecular evaluation. We conclude that in some patients with bartter syndrome type I, hypokalemia and/or metabolic alkalosis may be absent in the first years of life and persistent metabolic acidosis or hypernatremia and hyperchloremia may also be present. Molecular evaluation can definitely establish the diagnosis of atypical cases of this complex hereditary tubular disorder, which, in our experience, may exhibit phenotypic variability.- - - - - - - - - - ranking = 0.2keywords = dent (Clic here for more details about this article) |
4/28. Effect of Sar1-ala8-angiotensin ii on blood pressure and renin in Bartter's syndrome, before and after treatment with prostaglandin synthetase inhibitors.Three patients suffering from Bartter's syndrome were studied before and after 5 days of treatment with the prostaglandin synthetase inhibitors, aspirin and indomethacin. saralasin was given by intravenous infusion in increasing doses from 0.6 to 42 micrograms/min.kg/BW. During saralasin infusion a blood pressure reduction was observed in all patients. aspirin treatment did not affect this response and nor did it affect other manifestations of the syndrome. indomethacin treatment changed the blood pressure response to saralasin in such a way that the blood pressure was increased in one patient and was unchanged in the other. indomethacin also tended to normalize other features of Bartter's syndrome, such as the hyperreninaemia and angiotensin unresponsiveness, but did not affect the hypokalaemia. The saralsin effect on blood pressure is thus evidently inversely related to the prevailing activity of the renin-angiotensin system in this condition also, and the patients obviously depended on the renin-angiotensin system to maintain their blood pressure. Our findings, together with data in the literature, indicate that angiotensin unresponsiveness of the vascular bed is not a primary feature in Bartter's syndrome. Chloride loss is currently thought to be the basic abnormality and this may link the Bartter's syndrome with other diseased states characterized by chloride loss, such as the syndrome of habitual vomiting and chronic treatment with loop diuretics.- - - - - - - - - - ranking = 0.2keywords = dent (Clic here for more details about this article) |
5/28. Atypical bartter syndrome with sensorineural deafness with G47R mutation of the beta-subunit for ClC-Ka and ClC-Kb chloride channels, barttin.bartter syndrome comprises several related renal tubular disorders including classic Bartter, infantile Bartter (IBS), and gitelman syndrome. A new distinct group in bartter syndrome accompanied by sensorineural deafness (BSND) has been identified among the IBS patients. Recently a gene encoding an essential beta-subunit for ClC chloride channels, named barttin, with several mutations of the gene as the cause of BSND, has been described. We have observed a male who had not been diagnosed as bartter syndrome until 28 yr because of a mild clinical manifestation. The patient was affected with congenital deafness, which urged us to analyze his gene for barttin, and a mutation G47R, which was previously reported, has been identified. However, the clinical feature in the patient lacking the characteristic symptoms of IBS such as polyhydramnios, premature labor, or severe salt loss in neonatal period contrasts with that of the typical BSND patients described so far in the literature. This might be due to a less severe loss of function of barttin induced by G47R mutation, compared with others, and our observation seems to suggest a possibility of the prevalence of mild form BSND with various levels of barttin dysfunction among patients with congenital deafness of unknown origin.- - - - - - - - - - ranking = 0.4keywords = dent (Clic here for more details about this article) |
6/28. Heterozygous mutations of the gene for Kir 1.1 (ROMK) in antenatal bartter syndrome presenting with transient hyperkalemia, evolving to a benign course.Bartter-like syndrome encompasses a set of inherited renal tubular disorders associated with hypokalemic metabolic alkalosis, renal salt wasting, hyperreninemic hyperaldosteronism, and normal blood pressure. Antenatal bartter syndrome, a subtype of Bartter-like syndrome, is characterized by polyhydramnios, premature delivery, life-threatening episodes of fever and dehydration during the early weeks of life, growth retardation, hypercalciuria, and early-onset nephrocalcinosis. Mutations in the bumetanide-sensitive Na-K-2Cl cotransporter (NKCC2) and ATP-sensitive inwardly rectifying potassium channel (ROMK) of the thick ascending limb of Henle's loop have been identified in the antenatal bartter syndrome. We report the identification of two heterozygous mutations of the gene for Kir 1.1 (ROMK) from an antenatal bartter syndrome patient who presented at birth with mild salt wasting and a biochemical findings that mimicked primary pseudohypoaldosteronism type 1, such as hyperkalemia and hyponatremia, and evolved to a relatively benign course. We have identified amino acid exchanges Arg338Stop and Met357Thr in the gene exon 5 for ROMK by PCR and direct sequencing. Both mutations alter the C-terminus of the ROMK protein, and can affect channel function.- - - - - - - - - - ranking = 0.6keywords = dent (Clic here for more details about this article) |
7/28. Pseudo-bartter syndrome in a neonate on prostaglandin infusion.We describe a case of iatrogenic pseudo-bartter syndrome caused by administration of prostaglandin E1 (PGE1 alprostadil). Although the use of i.v. PGE1 is a well-established pharmacological therapy in neonates with a ductus-dependent congenital cardiopathy to ensure ductus-dependent flow, we could only find one other report on pseudo-bartter syndrome related to PGE1 infusion. CONCLUSION: Primary bartter syndrome is associated with endogenous increased levels of prostaglandins. Therefore, we postulate that the dose of prostaglandin E1 administered, immaturity and the genetic background are all relevant factors involved in the phenotypic presentation of iatrogenic pseudo-bartter syndrome in this preterm infant.- - - - - - - - - - ranking = 0.4keywords = dent (Clic here for more details about this article) |
8/28. Cardiac arrhythmias due to severe hypokalemia in a patient with classic Bartter disease.We report a young girl with classic Bartter disease (type III) with severe hypokalemia (< or = 2.0 mmol/l) who developed a prolonged heart rate-corrected QT interval of 510 ms (upper reference 430 ms) and ST segment depression in all leads. Holter electrocardiography was performed (with a plasma potassium level of 2.0 mmol/l) and it disclosed a stable sinus rhythm, a prolonged correct QT interval, more-evident ST segment depression during an increase in heart rate, a few single premature ventricular complexes, and nocturnal conduction abnormalities such as second-degree atrioventricular block 2:1. In the light of these results, the treatment was modified by increasing indomethacin from 1.5 to 3 mg/kg per day and adding spironolactone at a dose of 5 mg/kg per day. After 10 days, plasma potassium levels increased to 2.7 mmol/l and electrocardiographic abnormalities regressed. No other cardiac abnormalities were noted when the serum potassium was maintained > 2.5 mmol/l. In conclusion, this case report supports the link between arrhythmic events and chronic renal hypokalemic alkalosis in renal tubular disorders. We highlight the importance of standardizing the use of rest electrocardiography and 24-h Holter monitoring to diagnose arrhythmic events in children with severe hypokalemic renal disorders, especially in those with a plasma potassium < 2.5 mmol/l. The importance of beginning early medical treatment, to improve plasma potassium levels and reverse cardiac abnormalities, is emphasized.- - - - - - - - - - ranking = 0.2keywords = dent (Clic here for more details about this article) |
9/28. A novel splice site mutation of the thiazide-sensitive NaCl cotransporter gene in a Japanese patient with gitelman syndrome.gitelman syndrome (GS, MIM 263800) is an inherited disorder characterized by metabolic alkalosis with hypokalemia, hypomagnesemia, and hypocalciuria. The genetic abnormalities causing GS are known to lie in the thiazide-sensitive NaCl cotransporter (TSC), which is expressed in the distal tubule of the kidney. The TSC gene, located at chromosome 16, consists of 26 exons and encodes the protein containing 12 putative transmembrane domains with long intracellular amino and carboxy termini. Most of the abnormalities identified in GS were missense mutations, distributed throughout the TSC gene without a hot spot. A 42-year-old Japanese man was introduced for close examination of hypokalemia. In renal clearance studies using furosemide or thiazide, chloride clearance was increased after furosemide but not after thiazide administration. Furthermore, the distal fractional chloride reabsorption was dramatically decreased by furosemide but not thiazide administration, suggesting a defect in the distal tubule. We then analyzed the TSC gene to confirm the diagnosis of GS, and identified a novel G to T mutation at the acceptor splice site preceding exon 14, resulting in disruption of a conventional 3'AG consensus splice site. Abnormal splicing by this mutation is predicted to cause the formation of truncated TSC with a partial deletion of the transmembrane domain, which will loose the function of transporter. In conclusion, we have identified a unique novel splice site mutation of the TSC gene in GS. The predicted structure of this mutant TSC can conceivably cause an impairment of the transporter activity and thereby be responsible for the development of GS in our patient.- - - - - - - - - - ranking = 0.6keywords = dent (Clic here for more details about this article) |
10/28. Novel mutations of the chloride channel Kb gene in two Japanese patients clinically diagnosed as bartter syndrome with hypocalciuria.Hypokalemic metabolic tubulopathy, such as in bartter syndrome and gitelman syndrome, is caused by the dysfunction of renal electrolyte transporters. Despite advances in molecular genetics with regard to hypokalemic metabolic tubulopathy, recent reports have suggested that the phenotype-genotype correlation is still confusing, especially in classic Bartter and Gitelman syndromes. We report here two Japanese patients who suffered from clinically diagnosed classic bartter syndrome but who presented hypocalciuria. Hypocalciuria is generally believed to be a pathognomonic finding of NCCT malfunction. To better understand the genotype-phenotype correlation in these two cases, we screened four renal electrolyte transporter genes [Na-K-2Cl cotransporter (NKCC2), renal outer medullary K channel (ROMK), Cl channel Kb (ClC-Kb), and Na-Cl cotransporter (NCCT)] by the PCR direct sequencing method. We identified three ClC-Kb allelic variants, including two new mutations (L27R and W610X in patient 1 and a G to C substitution of a 3' splice site of intron 2 and W610X in patient 2). We did not find any mutations in the other three genes. Our present data suggest that some ClC-Kb mutations may affect calcium handling in renal tubular cells.- - - - - - - - - - ranking = 0.2keywords = dent (Clic here for more details about this article) |
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