Cases reported "Bartter Syndrome"

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1/27. Gitelman disease associated with growth hormone deficiency, disturbances in vasopressin secretion and empty sella: a new hereditary renal tubular-pituitary syndrome?

    Gitelman disease was diagnosed in two unrelated children with hypokalemic metabolic alkalosis and growth failure (a boy and a girl aged 7 mo and 9.5 y, respectively, at clinical presentation) on the basis of mutations detected in the gene encoding the thiazide-sensitive NaCl cotransporter of the distal convoluted tubule. GH deficiency was demonstrated by specific diagnostic tests in both children. Hypertonic saline infusion tests showed a partial vasopressin deficiency in the girl and delayed secretion of this hormone in the boy. magnetic resonance imaging revealed an empty sella in both cases. Up to now, hypomagnesemia and hypocalciuria have been considered obligatory criteria for the diagnosis of Gitelman disease; however, our two patients had hypomagnesemia and hypocalciuria in less than half the determinations. GH replacement treatment was associated with a good clinical response in both children. It appears that these cases represent a new phenotype, not previously described in Gitelman disease, and that the entity may be considered a new complex hereditary renal tubular-pituitary syndrome.
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2/27. Gitelman's syndrome (familial hypokalemia-hypomagnesemia).

    Gitelman's syndrome (GS) is a heritable renal disorder characterized by hypomagnesemia, hypokalemia and hypocalciuria, and distinct from Bartter's syndrome (BS). As compared to those with BS, patients with GS present at an older age, and they have a milder clinical picture, normal or slightly decreased concentrating ability, reduced urinary excretion of calcium, and permanently decreased serum magnesium level. GS is caused by defective NaCl transport in the distal convoluted tubule, and linked to the gene encoding the thiazide sensitive Na-Cl-cotransporter located on chromosome 16q. patients with BS, on the other hand, have mutations in the transporters in the thick ascending loop of henle (NKCC2, ROMK, and C1C-Kb). Treatment of GS consists of magnesium salt replacement. Long term prognosis in terms of maintaining growth, preserving renal function and life expectancy is excellent.
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3/27. Mimicry of surreptitious diuretic ingestion and the ability to make a genetic diagnosis.

    Gitelman's syndrome, also known as "hypocalciuric variant of Bartter's syndrome", is a cause of chronic hypokalemia and hypomagnesemia in adults. A specific gene has been found responsible for this disorder, encoding the thiazide-sensitive NaCl coporter (TSC) in the distal convoluted tubule. We describe a psychiatric patient with chronic symptomatic hypokalemia and hypomagnesemia whose electrolyte disturbances were subsequently misdiagnosed as an acute alcohol and benzodiazepine withdrawal syndrome, as chronic diuretic abuse and as a classical Bartter's syndrome. Finally, genetic investigation revealed the presence of mutations in the SLC12A3 gene leading to the proper diagnosis of Gitelman's syndrome. We emphasize that Gitelman's syndrome should be suspected in every hypokalemic patient with biochemical resemblance of diuretic ingestion, especially when repeated toxic screens for diuretics are negative. The ability to make a molecular-genetic diagnosis can be of practical benefit in confusing clinical settings.
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4/27. Distal nephron function in Bartter's syndrome: abnormal conductance to chloride in the cortical collecting tubule?

    Five patients with the clinical patterns of Bartter's syndrome underwent a series of clearance studies in order to characterize the underlying tubule defect. Free water generation during maximal water diuresis (CH2O), expressed as percentage of the distal delivery (CH2O CCl), was lower in the patients (72.5 /- 3.2%) than in controls (84.4 /- 5.5, p < 0.0001). During maximal water diuresis and furosemide administration (40 mg i.v. as bolus), NaCl reabsorption along the diluting nephron segments could be separated into 2 components, that occurring in the loop of henle (DRNaHL) and that occurring in tubule segments beyond the macula densa (DRNaDT): DRNaHL was normal, while DRNaDT was reduced (3.1 /- 0.8 vs. 6.2 /- 2.5 ml/min in controls, p < 0.015). Thus, according to this furosemide protocol, our patients had normal solute reabsorption in the loop of henle but reduced NaCl reabsorption in tubule segments beyond the macula densa. During 0.9% saline infusion (2 liters in 2 h, after stimulation of distal Na reabsorption with fludrocortisone) fractional excretion (FE) of K showed a linear rise with the increase of FECl-FEK, however, was much higher in the patients than in controls for every FECl level. In contrast, the infusion of Na2SO4, after fludrocortisone administration, induced similar FEK increases in patients and in controls. Thus, in these patients Na reabsorption in the distal nephron (possibly the cortical collecting tubule) was associated with the generation of a higher than normal electric potential gradient in the presence of Cl but not of another poorly reabsorbable anion, such as SO4(2-). These observations indicate that, in our patients, Henle's loop function is normal, while the collecting tubule function is abnormal. We suggest that NaCl wasting and enhanced tubular secretion of H and K in our patients might result from an abnormally low conductance to Cl in distal nephron site(s) where Na reabsorption is electrogenic, possibly the cortical collecting tubule. A larger than normal transtubular electric gradient would be generated by Na reabsorption, causing: (1) a direct stimulation of tubular secretion of K and H (leading to hypokalemia and alkalosis) and (2) inhibition of the reabsorption of Na ('trapped' into the tubular lumen by electric forces), with consequent extracellular volume contraction, hyperreninemia and hyperaldosteronism.
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5/27. Renal sodium handling study in an atypical case of Bartter's syndrome associated with mitochondriopathy and sensorineural blindness.

    Bartter's syndrome is a disorder that has been linked to mutations in one of three ion transporter proteins: NKCC2 (type I), ROMK (type II) and CCLNKB (type III), which affects a final common pathway that participates in ion transport by thick ascending limb cells. We present an atypical case of mitochondriopathy combined with tubule functional disturbances compatible with Bartter's syndrome and definitive sensorineural blindness. Our patient had a peculiar clinical presentation with signs of salt and volume depletion, low blood pressure and secondary hyperaldosteronism, associated with hypokalemic metabolic alkalosis, hypocalcemia and severe hypomagnesemia, uncommon in genetic forms of Bartter's syndrome. The enhanced absolute and fractional sodium excretion in our patient compared to volunteers was accompanied by increased post-proximal sodium rejection, suggesting a striking ion transport dysfunction in these nephron segments. These findings lead to the Bartter's syndrome diagnosis, accompanied by a suppose mitochondrial tick ascending loop of henle epithelium dysfunction that may reflect the high energy supplied by mitochondria electron transport chain, required for this nephron segment to maintain normal ion transport.
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6/27. 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.
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7/27. Acquired bartter-like syndrome associated with gentamicin administration.

    Although acute nonoliguric renal failure is a well-known nephrotoxic effect of aminoglycoside antibiotics, less recognized is acquired Bartter-like syndrome. Herein, we describe four female patients who presented with marked paresthesia, muscle weakness, and tetany following gentamicin therapy with total dose ranging from 1.2 g to 2.6 g. All were normotensive. Biochemical abnormalities included hypokalemia (K 1.8-2.3 mmol/L), metabolic alkalosis (HCO(3-) 31.9-34.2 mmol/L), hypomagnesemia (Mg2 0.9-1.2 mg/dL), hypermagnesiuria (fractional excretion of Mg 3-6%), hypocalcemia (free Ca2 2.0-4.1 mg/dL), and hypercalciuria (molar ratio of Ca2 /creatinine 0.23-0.53), all consistent with Bartter-like syndrome. serum immunoreactive parathyroid hormone concentration was low despite the hypocalcemia. The Bartter-like syndrome lasted for 2 to 6 weeks after cessation of gentamicin, coupled with supplementation of K , Ca2 , and Mg2 . These biochemical abnormalities resembled those seen in patients with gain-of-function mutations in the calcium-sensing receptor. We hypothesize that gentamicin, a polyvalent cationic molecule, induces the action of calcium-sensing receptor on the thick ascending loop of henle and distal convoluted tubule to cause renal wasting of Na , K , Cl-, Ca2 , and Mg2 .
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8/27. A rare case of Gitelman's syndrome presenting with hypocalcemia and osteopenia.

    Gitelman's syndrome (GS), an autosomal recessive disorder caused by a defect of the thiazide-sensitive Na-Cl cotransporter (TSC) at the distal tubule, is characterized by hyperreninemic hyperaldosteronism with normal or low blood pressure, hypokalemia, metabolic alkalosis, hypomagnesemia and hypocalciuria. An 18-yr-old Japanese man was admitted to our hospital with a history of muscle weakness and transient tetanic episodes. He showed hypocalcemia in addition to hypokalemia, severe hypomagnesemia, hypocalciuria and hyperreninemic hyperaldosteronism with normal blood pressure. Furthermore, bone mineral density at the lumbar spine revealed osteopenia. A diagnosis of GS was made on the basis of clinical features, laboratory data and renal function test. The electrolyte imbalance was corrected and bone mineral density was slightly increased with chronic treatment of magnesium and potassium salts. Genetic analysis revealed that TSC gene of the patient has a heterozygous C to A nucleotide substitution at position 545 in exon 4, which causes a threonine (Thr) to lysine (Lys) substitution at position 180. This is a rare case of GS with hypocalcemia and osteopenia which could be caused by severe hypomagnesemia.
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9/27. chondrocalcinosis secondary to hypomagnesemia in Gitelman's syndrome.

    chondrocalcinosis can be associated with hyperparathyroidism, hemochromatosis, hypophosphatasia, and hypomagnesemia. gitelman syndrome (GS), an inherited disorder due to loss of function mutations of the gene encoding the distal convoluted tubule Na-Cl cotransporter (NCCT), is characterized by hypokalemia metabolic alkalosis, hypomagnesemia, and hypocalciuria. A 53-year-old man, with history of recurrent joint effusions and pains affecting knees and wrists, had transient episodes of muscle pain, weakness, cramping, and fatigue over a one-year period. Laboratory tests showed hypokalemia, metabolic alkalosis, hypocalciuria, and hypomagnesemia related to genetically proven GS. Radiographs of affected joints revealed calcium pyrophosphate dihydrate deposition. This observation points out the necessity to look for Mg depletion (and especially GS) in the biological investigation of chondrocalcinosis. Additionally, the association between GS (NCCT inactivation) and high bone mineral density provides a new insight into the possible role of thiazides in osteoporosis management.
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10/27. Simultaneous mutations in the CLCNKB and SLC12A3 genes in two siblings with phenotypic heterogeneity in classic bartter syndrome.

    Two siblings (brother and sister) with renal tubular hypokalemic alkalosis underwent clinical, biochemical and molecular investigations. Although the biochemical findings were similar (including hypokalemia, metabolic alkalosis, hyperreninemia, hyperaldosteronism and normal blood pressure), the clinical findings were different: the boy, who also presented syndromic signs, developed glomerular proteinuria and renal biopsy revealed focal segmental glomerular sclerosis; the girl showed the typical signs of classic bartter syndrome. As described in a previous paper, a heterozygous mutation (frameshift 2534delT) was demonstrated in the gene encoding the thiazide-sensitive NaCl co-transporter (SLC12A3) of the distal convoluted tubule; the second molecular analysis revealed a compound heterozygous mutation (A61D/V149E) in the CLCNKB chloride channel gene in both subjects, inherited in trans from the parents. The children were finally diagnosed as having classic bartter syndrome. These cases represent the first report of the simultaneous presence of heterozygous and compound heterozygous mutations in the SLC12A3 and CLCNKB genes, both of which are involved in renal salt losing tubulopathies, and confirm previous observations regarding classic bartter syndrome phenotype variability in the same kindred.
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