The pathogenetic spectrum of Bartter's syndrome

Diagnosis and management of Bartter syndrome: executive summary of the consensus and recommendations from the European Rare Kidney Disease Reference Network Working Group for Tubular Disorders

Bartter syndrome is a rare inherited salt-losing renal tubular disorder characterized by secondary hyperaldosteronism with hypokalemic and hypochloremic metabolic alkalosis and low to normal blood pressure. The primary pathogenic mechanism is defective salt reabsorption predominantly in the thick ascending limb of the loop of Henle. There is significant variability in the clinical expression of the disease, which is genetically heterogenous with 5 different genes described to date. Despite considerable phenotypic overlap, correlations of specific clinical characteristics with the underlying molecular defects have been demonstrated, generating gene-specific phenotypes. As with many other rare disease conditions, there is a paucity of clinical studies that could guide diagnosis and therapeutic interventions. In this expert consensus document, the authors have summarized the currently available knowledge and propose clinical indicators to assess and improve quality of care.

A novel compound heterozygous KCNJ1 gene mutation presenting as late-onset Bartter syndrome: Case report

RATIONALE

Bartter syndrome is an autosomal-recessive inherited disease in which patients present with hypokalemia and metabolic alkalosis. We present 1 case with Bartter syndrome, due to a novel compound heterozygous mutation in the KCNJ1 gene encoding the ATP-sensitive inward rectifier potassium channel in the thick ascending limb of the loop of Henle.

PATIENT CONCERNS

A patient was admitted to our hospital because of weakness, polyuria, and polydipsia. At presentation to our hospital, the female Chinese patient was 34 years old and her physical examination was normal. Laboratory studies revealed hypokalemia, metabolic alkalosis, hypercalciuria, hyperparathyroidemia, and hyper-reninemia. In addition, urinary potassium was obviously higher. Computer tomography scan confirmed the patient had the bilateral medullary nephrocalcinosis.

DIAGNOSIS

Blood samples were received from the patient and her parents, and deoxyribonucleic acid was extracted. The genetic analysis of SLC12A1, SLC12A3, KCNJ1, CLCNKB, BSND, and CASR was performed. The compound heterozygous KCNJ1 gene mutation was validated using conventional Sanger sequencing methods.

INTERVENTIONS

The patient was treated with potassium supplementation. Her blood and urine chemistries improved over the next week. Serum potassium normalized with improvement in polyuria and polydipsia over the next month.

OUTCOMES

Our patient was compound heterozygous for Thr234Ile and Thr71Met in the KCNJ1 gene. The c.701C>T variant predicted a change from a threonine codon to an isoleucine codon (p.Thr234Ile). The c.212C>T variant predicted a change from a threonine codon to a methionine codon (p.Thr71Met). The unaffected mother was heterozygous for the Thr234Ile mutation, whereas unaffected father was heterozygous for the Thr71Met mutation.

LESSONS

The phenotypes of the patient were similar to other patients with Bartter syndrome. The phenotypes of the patient could eventually be explained by the presence of the novel compound heterozygous p.Thr234Ile/p.Thr71Met variants in the KCNJ1 gene.

Transient Antenatal Bartter's Syndrome: A Case Report

Antenatal Bartter's syndrome is a rare inherited disorder characterized by fetal polyhydramnios and polyuria that is usually detected between 24 and 30 weeks of gestation. However, a rare, severe, but transient form of antenatal Bartter's syndrome due to an x-linked melanoma-associated antigen D2 (MAGED2) mutation has recently been described. This transient type results in the earlier onset of severe polyhydramnios and preterm birth, but spontaneously resolves postnatally. Here, we present a case of a 29-week gestation male born to a mother with severe polyhydramnios, who was subsequently found to have a novel mutation for MAGED2 not previously reported. This is the first and only case not to be treated with indomethacin, yet still resulted in spontaneous resolution of symptoms. Our case suggests the need for awareness of and testing for this new mutation in cases of severe antenatal polyhydramnios and discusses the perinatal treatment of this condition.

A novel variant in the SLC12A1 gene in two families with antenatal Bartter syndrome

AIM

Bartter syndrome is an autosomal-recessive inherited disease in which patients present with hypokalaemia and metabolic alkalosis. We present two apparently nonrelated cases with antenatal Bartter syndrome type I, due to a novel variant in the SLC12A1 gene encoding the bumetanide-sensitive sodium-(potassium)-chloride cotransporter 2 in the thick ascending limb of the loop of Henle.

METHODS

Blood samples were received from the two cases and 19 of their relatives, and deoxyribonucleic acid was extracted. The coding regions of the SLC12A1 gene were amplified using polymerase chain reaction, followed by bidirectional direct deoxyribonucleic acid sequencing.

RESULTS

Each affected child in the two families was homozygous for a novel inherited variant in the SLC12A1gene, c.1614T>A. The variant predicts a change from a tyrosine codon to a stop codon (p.Tyr538Ter). The two cases presented antenatally and at six months of age, respectively.

CONCLUSION

The two cases were homozygous for the same variant in the SLC12A1 gene, but presented clinically at different ages. This could eventually be explained by the presence of other gene variants or environmental factors modifying the phenotypes. The phenotypes of the patients were similar to other patients with antenatal Bartter syndrome.

Molecular pathophysiology of Bartter's and Gitelman's syndromes

BACKGROUND

In the last two decades, progress in cytogenetic and genome research has enabled investigators to unravel the underlying molecular mechanisms of inherited tubulopathies such as Bartter's and Gitelman's syndromes and helped physicians to better understand not only these two pathologic entities but also renal pathophysiology and salt sensitive hypertension.

DATA SOURCES

Articles collected from PubMed and open access journals included original articles, research articles, and comprehensive reviews. They were evaluated by the authors with an special emphasis on originality and up to date information about molecular pathophysiology.

RESULTS

Bartter's and Gitelman's syndromes are two different inherited salt loosing tubulopathies. They are characterized by various inability of distal nephron to reabsorb sodium chloride with resultant extarcellular volume contraction and increased activity of the renin angiotensin aldosterone system. Hypokalemic metabolic alkalosis is a common feature of these two forms of tubulopathies. Hypercalciuria characterizes the majority of Bartter's syndrome, and hypomagnesemia with hypocalciuria characterizes Gitelman's syndrome. Low blood pressure is a common feature among patients who suffered from these tubulopathies. Bartter's syndromes encompass a heterogeneous group of ion channels defects localized at the thick ascending limp of Henle's loop with resultant loss of function of sodium-potassium-2 chloride cotransporter. These defects result in the impairment of the countercurrent multiplication system of the kidney as well as calcium, potassium and acid base disturbances which in the majority of cases are proved lethal especially in the antenatal and/or immediate postnatal life period. The underlying pathology in Gitelman's syndrome is defined to the distal convoluted tubule and is related to loss of function of the sodium-chloride cotransporter. The results of this defect encompass the inability of extracellular volume homeostasis, magnesium and potassium conservation, and acid base disturbances which are generally mild and in the majority of cases are not life-threatening.

CONCLUSIONS

Recent advances in molecular pathophysiology of Bartter's and Gitelman's syndromes have helped physicians to better understand the underlying mechanisms of these pathologic entities which remain obscure. Data collected from experiments among genetically manipulated animals enable us to better understand the pathophysiology of mammalian kidney and the underlying mechanisms of salt sensitive hypertension and to lay a foundation for the future development of new drugs, especially diuretics and antihypertensive drugs.

Pregnancy in a patient with gouty arthritis secondary to pseudo-Bartter syndrome

A 32-year-old woman with pseudo-Bartter syndrome secondary to excessive use of laxatives, presented with hypokalemia, metabolic alkalosis, hyperuricemia, and gouty arthritis with tophi. Subsequently the patient became pregnant and displayed recurrent severe gouty flares of multiple joints. Monosodium urate crystals were aspirated from the knee confirming the diagnosis of gout. Previous reports have stated an association between Bartter syndrome and gout, but this is the first case report of a pregnancy with active gouty arthritis combined with pseudo-Bartter syndrome.

Problems in diagnosing atypical Gitelman's syndrome presenting with normomagnesaemia

OBJECTIVE

Gitelman's syndrome, recognized as a variant of Bartter's syndrome, is characterized by hypokalaemic metabolic alkalosis in combination with hypomagnesaemia and hypocalciuria. Overlapping biochemical features in Gitelman's syndrome and Bartter's syndrome has been observed. Here, we investigated the clinical, biochemical, and genetic characteristics of five, chronic, nonhypertensive and hypokalaemic Japanese patients.

METHODS

Serum and urinary electrolytes, plasma renin activity and plasma aldosterone concentration were measured in five patients (four males and one female) with hypokalaemia. Renal clearance tests were performed and distal fractional chloride reabsorption calculated. Finally, mutational analysis of the thiazide-sensitive Na-Cl co-transporter gene was performed.

RESULTS

Symptoms in patients varied from mild (muscle weakness and numbness) to severe (tetany and foot paralysis). All patients were normotensive or hypotensive, and all had hypokalaemia, hypocalciuria, and hyperreninaemic hyperaldosteronism. However, two male patients had normomagnesaemia, while the remainder was hypomagnesaemic. Renal clearance tests showed that the administration of furosemide decreased distal fractional chloride reabsorption, while thiazide ingestion failed to decrease it. Genetic analysis identified six thiazide-sensitive Na-Cl co-transporter gene mutations, including two novel ones. Therefore, on the basis of the confirmatory renal clearance tests and mutational analysis, a diagnosis of Gitelman's syndrome was made in these patients.

CONCLUSIONS

Two of the five patients diagnosed with Gitelman's syndrome were normomagnesaemic, which is uncommon in this syndrome. Our study indicates that renal clearance tests and mutation analysis can play an important role in diagnosing Gitelman's syndrome more precisely.

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.

Identification of novel mutations in Na-Cl cotransporter gene in a Korean patient with atypical Gitelman's syndrome

The authors report the case of a 20-year-old man with unexplained hypokalemia and metabolic alkalosis suggesting hypokalemic tubulopathy. Interestingly, he showed a mixed phenotype of Gitelman's syndrome (GS) and Bartter's syndrome, which includes normomagnesemia, normal renal magnesium excretion, and hypocalciuria. Renal clearance study showed the presence of a critical defect in the distal nephron rather than loop of Henle. Further family study showed that his mother had a definitive phenotype of GS. By the molecular genetic analysis of these patients, 7 different mutations of the NCCT gene were identified consisting of 3 missense, 1 splice site, and 3 silent mutations. Four of these mutations were novel. The authors emphasize that the combination of a molecular genetic approach and renal clearance study could be of practical benefit in confusing clinical setting and support new diagnostic criteria in GS.

Absence of small conductance K+ channel (SK) activity in apical membranes of thick ascending limb and cortical collecting duct in ROMK (Bartter's) knockout mice

The ROMK (Kir1.1; Kcnj1) gene is believed to encode the apical small conductance K(+) channels (SK) of the thick ascending limb (TAL) and cortical collecting duct (CCD). Loss-of-function mutations in the human ROMK gene cause Bartter's syndrome with renal Na(+) wasting, consistent with the role of this channel in apical K(+) recycling in the TAL that is crucial for NaCl reabsorption. However, the mechanism of renal K(+) wasting and hypokalemia that develop in individuals with ROMK Bartter's syndrome is not apparent given the proposed loss of the collecting duct SK channel. Thus, we generated a colony of ROMK null mice with approximately 25% survival to adulthood that provides a good model for ROMK Bartter's syndrome. The remaining 75% of null mice die in less than 14 days after birth. The surviving ROMK null mice have normal gross renal morphology with no evidence of significant hydronephrosis, whereas non-surviving null mice exhibit marked hydronephrosis. ROMK protein expression was absent in TAL and CCD from null mice but exhibited normal abundance and localization in wild-type littermates. ROMK null mice were polyuric and natriuretic with an elevated hematocrit consistent with mild extracellular volume depletion. SK channel activity in TAL and CCD was assessed by patch clamp analysis in ROMK wild-type ROMK(+/+), heterozygous ROMK(+/-), and null ROMK(-/-) mice. In 313 patches with successful seals from the three ROMK genotypes, SK channel activity in ROMK (+/+ and +/-) exhibited normal single channel kinetics. The expression frequencies are as follows: 67 (TAL) and 58% (CCD) in ROMK(+/+); about half that of the wild-type in ROMK(+/-), being 38 (TAL) and 25% (CCD); absent in both TAL or CCD in ROMK(-/-) between 2 and 5 weeks in 15 mice (61 and 66 patches, respectively). The absence of SK channel activity in ROMK null mice demonstrates that ROMK is essential for functional expression of SK channels in both TAL and CCD. Despite loss of ROMK expression, the normokalemic null mice exhibited significantly increased kaliuresis, indicating alternative mechanisms for K(+) absorption/secretion in the nephron.

Clinical presentation of genetically defined patients with hypokalemic salt-losing tubulopathies

PURPOSE

Hypokalemic salt-losing tubulopathies (Bartter-like syndromes) comprise a set of clinically and genetically distinct inherited renal disorders. Mutations in four renal membrane proteins involved in electrolyte reabsorption have been identified in these disorders: the furosemide-sensitive sodium-potassium-chloride cotransporter NKCC2, the potassium channel ROMK, the chloride channel ClC-Kb, and the thiazide-sensitive sodium-chloride cotransporter NCCT. The aim of this study was to characterize the clinical features associated with each mutation in a large cohort of genetically defined patients.

PATIENTS AND METHODS

The phenotypic characteristics of 65 patients with molecular defects in NKCC2, ROMK, ClC-Kb, or NCCT were collected retrospectively.

RESULTS

ROMK and NKCC2 patients presented with polyhydramnios, nephrocalcinosis, and hypo- or isosthenuria. Hypokalemia was less severe in the ROMK patients compared with the NKCC2 patients. In contrast, NCCT patients had hypocalciuria, hypomagnesemia, and marked hypokalemia. While this dissociation of renal calcium and magnesium handling was also observed in some ClC-Kb patients, a few ClC-Kb patients presented with hypercalciuria and hypo- or isosthenuria.

CONCLUSIONS

ROMK, NKCC2, and NCCT mutations usually have uniform clinical presentations, whereas mutations in ClC-Kb occasionally lead to phenotypic overlaps with the NCCT or, less commonly, with the ROMK/NKCC2 cohort. Based on these results, we propose an algorithm for the molecular diagnosis of hypokalemic salt-losing tubulopathies.

Inherited primary renal tubular hypokalemic alkalosis: a review of Gitelman and Bartter syndromes

Inherited hypokalemic metabolic alkalosis, or Bartter syndrome, comprises several closely related disorders of renal tubular electrolyte transport. Recent advances in the field of molecular genetics have demonstrated that there are four genetically distinct abnormalities, which result from mutations in renal electrolyte transporters and channels. Neonatal Bartter syndrome affects neonates and is characterized by polyhydramnios, premature delivery, severe electrolyte derangements, growth retardation, and hypercalciuria leading to nephrocalcinosis. It may be caused by a mutation in the gene encoding the Na-K-2Cl cotransporter (NKCC2) or the outwardly rectifying potassium channel (ROMK), a regulator of NKCC2. Classic Bartter syndrome is due to a mutation in the gene encoding the chloride channel (CLCNKB), also a regulator of NKCC2, and typically presents in infancy or early childhood with failure to thrive. Nephrocalcinosis is typically absent despite hypercalciuria. The hypocalciuric, hypomagnesemic variant of Bartter syndrome (Gitelman syndrome), presents in early adulthood with predominantly musculoskeletal symptoms and is due to mutations in the gene encoding the Na-Cl cotransporter (NCCT). Even though our understanding of these disorders has been greatly advanced by these discoveries, the pathophysiology remains to be completely defined. Genotype-phenotype correlations among the four disorders are quite variable and continue to be studied. A comprehensive review of Bartter and Gitelman syndromes will be provided here.

Pregnancy complicated with Bartter's syndrome: a case report

Bartter's syndrome is a rare renal disorder, and since there are few case reports of Bartter's syndrome complicating pregnancy are few, the changes of electrolytes and hormonal metabolism during pregnancy are unknown. We describe and discuss the course of pregnancy complicated with Bartter's syndrome.

[Genetic hypokalemia]

INTRODUCTION

Hypokalemia is the most frequent electrolytic disturbance in hospitalized patients. It is sometimes familial. Careful clinical and biological evaluation may guide further genetic analysis.

CURRENT KNOWLEDGE AND KEY POINTS

Genetic hypokalemia is linked to disorders of mineralocorticoid hormone synthesis or action (glucocorticoid-remediable hyperaldosteronism, congenital adrenal hyperplasia, apparent excess of mineralocorticoids), to renal tubular disorders (Liddle's syndrome, Bartter's and Gitelmann's syndrome, tubular acidosis) or to disorders of cellular transfer of potassium (hypokalemic periodic paralysis).

FUTURE PROSPECTS AND PROJECTS

Molecular mechanisms of adult Bartter's syndrome are probably different from pediatric syndromes. A better clinical and biological evaluation with longitudinal follow-up could allow significant progress in the knowledge of the natural history and prognosis of these syndromes.

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.

The pathophysiological and molecular basis of Bartter's and Gitelman's syndromes

Molecular defects affecting the transport of sodium, potassium and chloride in the nephron through the ROMK K+ channel, Na+/K+/2Cl- cotransporter, the Na+/Cl- cotransporter and chloride channel have been identified in patients with Bartter's and Gitelman's syndromes. Defects of the angiotensin II type I receptor and CFTR have also being described. These defects are simple (i.e., most are single amino acid substitutions) but affect key elements in tubular transport. The simplicity of the genetic defects may explain why the inheritance of these conditions remains unclear in most kindreds (i.e., not just recessive or dominant) and emphasises the crucial importance of the conformational structure of these channels. Application of this molecular information will allow the early genetic identification of patients with these syndromes and enable us to differentiate between the various disorders at a functional level. It may also identify a subgroup in which the heterozygous form may make patients potentially exquisitely sensitive to diuretics.

Recombinant human growth hormone and Gitelman's syndrome

Gitelman's syndrome is a primary renal tubular disorder with hypokalemic metabolic alkalosis, hypocalciuria, and magnesium deficiency. Short stature is one of clinical manifestations in children. The pathogenesis of short stature in Gitelman's syndrome is not known. To evaluate whether growth hormone (GH) is deficient and whether recombinant human GH (rhGH) improves growth rate, rhGH therapy was tried in a child with Gitelman's syndrome. Both height and body weight were less than the third percentile. Laboratory and radiologic findings suggested GH deficiency. During the first 6 months, rhGH therapy with potassium supplement markedly elevated growth rate from 3.8 cm/yr to 12.0 cm/yr. After cessation of rhGH, height increment markedly decreased to the pretreatment level of 3.6 cm/yr during the second 6 months. Additionally, hypomagnesemia was corrected after rhGH therapy. Accordingly, GH deficiency may contribute to short stature in children with Gitelman's syndrome, and rhGH therapy would be an excellent adjunctive treatment for short children with Gitelman's syndrome whose condition is resistant to conventional therapies in terms of growth.

Bartter syndrome: unraveling the pathophysiologic enigma

Familial hypokalemic, hypochloremic metabolic alkalosis, or Bartter syndrome, is not a single disorder but rather a set of closely related disorders. These Bartter-like syndromes share many of the same physiologic derangements, but differ with regard to the age of onset, the presenting symptoms, the magnitude of urinary potassium (K) and prostaglandin excretion, and the extent of urinary calcium excretion. At least three clinical phenotypes have been distinguished: (1) classic Bartter syndrome; (2) the hypocalciuric-hypomagnesemic Gitelman variant; and (3) the antenatal hypercalciuric variant (also termed hyperprostaglandin E syndrome). The fundamental pathogenesis of this complex set of disorders has long fascinated and stymied investigators. Physiologic investigations have suggested numerous pathogenic models. The cloning of genes encoding renal transport proteins has provided molecular tools to begin testing these hypotheses. To date, molecular genetic analyses have determined that mutations in the gene encoding the thiazide-sensitive sodium-chloride (Na-Cl) cotransporter underlie the pathogenesis of the Gitelman variant. In comparison, the antenatal variant is genetically heterogeneous with mutations in the genes encoding either the bumetanide-sensitive sodium-potassium-chloride (Na-K-2Cl) cotransporter or the luminal, ATP-regulated, K channel. With these data, investigators have begun to unravel the pathophysiologic enigma of the Bartter-like syndromes. Further studies will help refine pathogenic models for this set of disorders as well as provide new insights into the normal mechanisms of renal electrolyte transport.

Linkage of infantile Bartter syndrome with sensorineural deafness to chromosome 1p

Bartter syndrome (BS) is a family of disorders manifested by hypokalemic hypochloremic metabolic alkalosis with normotensive hyperreninemic hyperaldosteronism. We evaluated a unique, inbred Bedouin kindred in which sensorineural deafness (SND) cosegregates with an infantile variant of the BS phenotype. Using a DNA-pooling strategy, we screened the human genome and successfully demonstrated linkage of this unique syndrome to chromosome 1p31. The genes for two kidney-specific chloride channels and a sodium/hydrogen antiporter, located near this region, were excluded as candidate genes. Although the search for the disease-causing gene in this family continues, this linkage further demonstrates the genetic heterogeneity of BS. In addition, the cosegregation of these phenotypes allows us to postulate that a single genetic alteration may be responsible for the SND and the BS phenotype. The identification and characterization of this gene would lead to a better understanding of the normal physiology of the kidney and the inner ear.

Flow diagrams for the diagnosis of acid-base disorders

This article discusses flow diagrams and tables intended to provide a systematic approach to the rapid laboratory differential diagnosis of acid-base disorders in the emergency department.

Renal magnesium handling: new insights in understanding old problems

Recent research has provided new concepts in our understanding of renal magnesium handling. Although the majority of the filtered magnesium is reabsorbed within the loop of Henle, it is now recognized that the distal tubule also plays an important role in magnesium conservation. Magnesium absorption within the cTAL segment of the loop is passive and dependent on the transepithelial voltage. Magnesium transport in the DCT is active and transcellular in nature. Many of the hormonal (PTH, calcitonin, glucagon, AVP) and nonhormonal (magnesium-restriction, acid-base changes, potassium-depletion) influences that affect magnesium transport within the cTAL similarly alter magnesium absorption within the DCT. However, the cellular mechanisms are different. Actions within the loop affect either the transepithelial voltage or the paracellular permeability. Influences acting in the DCT involve changes in active transcellular transport either Mg2+ entry across the apical membrane or Mg2+ exit from the basolateral side. These transport processes are fruitful areas for future research. An additional regulatory control has recently been recognized that involves an extracellular Ca2+/Mg(2+)-sensing receptor. This receptor is present in the basolateral membrane of the TAL and DCT and modulates magnesium and calcium conservation with elevation in plasma divalent cation concentration. Further studies are warranted to determine the physiological role of the Ca2+/Mg(2+)-sensing receptor, but activating and inactivating mutations have been described that result in renal magnesium-wasting and hypermagnesemia, respectively. All of these receptor-mediated controls change calcium absorption in addition to magnesium transport. Selective magnesium control is through intrinsic control of Mg2+ entry into distal tubule cells. The cellular mechanisms that intrinsically regulate magnesium transport have yet to be described. Familial diseases associated with renal magnesium-wasting provide a unique opportunity to study these intrinsic controls. Loop diuretics such as furosemide increase magnesium excretion by virtue of its effects on the transepithelial voltage thereby inhibiting passive magnesium absorption. Distally acting diuretics, like amiloride and chlorothiazide, enhance Mg2+ entry into DCT cells. Amiloride may be used as a magnesium-conserving diuretic whereas chlorothiazide may lead to potassium-depletion that compromises renal magnesium absorption. Patients with Bartter's and Gitelman's syndromes, diseases of salt transport in the loop and distal tubule, respectively, are associated with disturbances in renal magnesium handling. These may provide useful lessons in understanding segmental control of magnesium reabsorption. Metabolic acidosis diminishes magnesium absorption in MDCT cells by protonation of the Mg2+ entry pathway. Metabolic alkalosis increases magnesium permeability across the cTAL paracellular pathway and stimulates Mg2+ entry into DCT cells. Again, these changes are likely due to protonation of charges along the paracellular pathway of the cTAL and the putative Mg2+ channel of the DCT. Cellular potassium-depletion diminishes the voltage-dependent magnesium absorption in the TAL and Mg2+ entry into MDCT cells. However, the relationship between potassium and magnesium balance is far from clear. For instance, magnesium-wasting is more commonly found in patients with Gitelman's disease than Bartter's but both have hypokalemia. Further studies are needed to sort out these discrepancies. Phosphate deficiency also decreases Mg2+ uptake in distal cells but it apparently does so by mechanisms other than those observed in potassium depletion. Accordingly, potassium depletion, phosphate deficiency, and metabolic acidosis may be additive. The means by which cellular potassium and phosphate alter magnesium handling are unclear. Research in the nineties has increased our understanding of renal magnesium transport and regulation, but there are many in

Studies on the site of renal tubular defect in Bartter's syndrome

Renal tubular function was studied in an 8-month-old male infant with Bartter's syndrome, which is characterized by hypokalemic metabolic alkalosis, normotensive hyperreninemic hyperaldosteronism, and reduced pressor response to angiotensin II. Chloride transport along the diluting segment (CH2O/CH2O + CCl) was impaired. Furthermore, furosemide did not elicit normal natriuresis, which suggested impaired chloride reabsorptive capacity at the furosemide-sensitive ascending limb of Henle's loop. Loss of antidiuretic hormone-mediated urinary concentration was in support of this. These findings pointed to the thick ascending limb of Henle's loop as the site of the primary defect in this child.

Bartter's syndrome, supraventricular tachycardia, mitral valve prolapse, and asthma: a therapeutic challenge

A 25-year-old man with acquired Bartter's syndrome, mitral valve prolapse, and supraventricular tachycardia secondary to a low atrial focus was diagnosed with asthma. The unique aspects of managing these coexisting diseases are evaluated. Calculation of free-water clearance in the diagnosis of Bartter's syndrome and the etiology and characteristics of the syndrome are discussed.

Hypokalemic metabolic alkalosis with hypomagnesuric hypermagnesemia and severe hypocalciuria: a new syndrome?

Bartter's and Gitelman's syndromes are characterized by hypokalemia, urinary potassium wasting, elevated plasma renin activity and aldosterone levels, normotension, and prostaglandinuria. They differ in that hypomagnesemia and hypocalciuria are universal in Gitelman's syndrome; 20% of cases of Bartter's syndrome have hypomagnesemia and hypercalciuria. We present a 44-year-old white man referred for hypokalemia. Clinical evaluation was unremarkable. He had hypokalemia (P(K), 2.8 to 3.0 mEq/L), hypochloremic metabolic alkalosis, mild azotemia (serum creatinine, 1.4 to 1.8 mg/dL; creatinine clearance, 59 mL/min), normocalcemia, marked persistent hypocalciuria (FE(Ca), 0.08% to 0.09%), and normal intact parathyroid hormone levels (51 pg/mL) and glucosuria. He had persistent hypermagnesemia (P(Mg), 2.1 to 2.8 mEq/L) with relative hypomagnesuria (FE(Mg), 3.2% to 5.2%) given the level of renal impairment and hypermagnesemia. Supine plasma renin activity and aldosterone levels were high (11 ng/mL/hr and 43 ng/dL, respectively). An excessive dietary intake of magnesium, including medications, was excluded. Studies were performed after withdrawing all medications for 8 days. A maximum water diuresis was established (an oral load of 20 mL/kg; stable Uosm, 120 mOsm/kg), and free water and solute clearances were studied at baseline and after sequential intravenous injections of 125 mg chlorothiazide and 40 mg furosemide. The patient had moderate renal impairment (technetium diethylene triamine pentacetic acid [DTPA] clearance, 35.4 mL/min/1.73 m2) and, in contradistinction to Bartter's and Gitelman's syndromes, sodium and water handling in the thick ascending limb of the loop of Henle and the distal tubule (fractional distal solute reabsorption) was normal, but there was evidence of a defect in the proximal tubule reabsorption (glucosuria, supranormal C(H2O) and high distal delivery). Hypomagnesuria and hypocalciuria appeared to be secondary to an increase in their absorption in the loop of Henle (increased excretion following furosemide). In conclusion, this combination of metabolic abnormalities has never been described. We postulate a proximal tubular defect in the absorption of NaCl leading to hypocalciuria, hypomagnesuria, and potassium wasting. Whether the tubular defect is primary or secondary to a renal parenchymal disease is, however, unclear.

Impaired response to furosemide in hyperprostaglandin E syndrome: evidence for a tubular defect in the loop of Henle

In hyperprostaglandin E syndrome (HPS) renal wasting of electrolytes and water is consistently associated with enhanced synthesis of prostaglandin E2. In contrast to Bartter or Gitelman syndrome (BS/GS), HPS is characterized by its severe prenatal manifestation, leading to fetal polyuria, development of polyhydramnios, and premature birth. This disorder mimics furosemide treatment with hypokalemic alkalosis, hypochloremia, isosthenuria, and impaired renal conservation of both calcium and magnesium. Therefore the thick ascending limb of the loop of Henle seems to be involved in HPS. To characterize the tubular defect we investigated the response to furosemide (2 mg/kg) in HPS (n = 8) and BS/GS (n = 3) 1 week after discontinuation of long-term indomethacin treatment. Sensitivity to furosemide was completely maintained in patients with BS/GS. The diuretic, saluretic, and hormonal responses were similar to those of a control group of healthy children (n = 13), indicating an intact function of the thick ascending limb of the loop of Henle in BS/GS. In contrast, patients with HPS had a marked resistance to this loop diuretic. Furosemide treatment increased urine output by 7.5 +/- 0.7 ml/kg per hour in healthy control subjects but only by 4.4 +/- 1.2 ml/kg per hour (p < 0.5) in children with HPS. In parallel, the latter also had a markedly impaired saluretic response (delta Cl(urine) 0.14 +/- 0.04 mmol/kg per hour vs 0.85 +/- 0.09 mmol/kg per hour, p < 0.001; delta Na(urine) 0.23 +/- 0.06 mmol/kg per hour vs 0.77 +/- 0.09 mmol/kg per hour, p < 0.001). Furosemide therapy further enhanced prostaglandin E2 excretion in patients with HPS (54 +/- 17 to 107 +/- 28 ng/hr per 1.73 m2, p < 0.05), whereas no significant effect was observed in healthy children (20 +/- 3 to 12 +/- 3 ng/hr per 1.73 m2). We conclude that a defect of electrolyte reabsorption in the thick ascending limb of the loop of Henle plays a major role in HPS.

Gitelman's syndrome is genetically distinct from other forms of Bartter's syndrome

In the past the term Bartter's syndrome has been used to describe a spectrum of inherited renal tubular disorders with hypokalemic metabolic alkalosis and overlapping and additional clinical and biochemical features. Pathogenesis remained uncertain until recently Gitelman's syndrome, the hypokalemic-hypomagnesemic variant with hypocalciuria, was linked to the gene encoding the thiazide-sensitive Na-Cl-cotransporter (TSC) located on chromosome 16q. Various mutations in the TSC gene were identified in patients with Gitelman's syndrome. To clarify whether different forms of hypokalemic tubular disorders (HTD) represent variable phenotypes of a common genetic defect, we performed linkage analyses in 17 families with different symptoms of HTD with four highly polymorphic chromosome 16 DNA markers closely linked to the TSC gene. Linkage of Gitelman's syndrome to the TSC locus was confirmed in our families with a maximum two-point Lod score Z = 4.70 (theta = 0.001) for marker locus D16S526. Highly negative LOD scores were obtained at this locus in our families with classic Bartter's syndrome (Z = 9.89, theta = 0.001) and hyperprostaglandin E syndrome (Z = -11.24, theta = 0.001). Our data prove that Gitelman's syndrome is genetically distinct from classic Bartter's syndrome and hyperprostaglandin E syndrome. It remains unknown if classic Bartter's syndrome and hyperprostaglandin E syndrome are caused by a common genetic defect.

Renal sonographic patterns in Bartter's syndrome

The renal sonographic findings in ten cases of Bartter s syndrome investigated at the King Khalid University Hospital, Riyadh, Saudi Arabia are described. There were various sonographic abnormalities other than those of hyperechoic pyramids as previously described. These were diffuse increased renal echogenicity and hyperechoic echogenicity in the kidneys with the exception of the pyramids. This condition can be suspected early if nephrocalcinosis is present in a child with a history of polyhydramnios and premature delivery.

Bartter's Syndrome Associated with Severe Retinopathy and Presenting as Pseudohypoaldosteronism in a Newborn

Various pathophysiological explanations for Bartter's syndrome have been put forward since the condition was first described in 19621. It is currently thought that reduced reabsorbtion of sodium chloride in the distal tubule of the loop of Henle and the collecting ducts leads to secondary hyperkaluria and hypokalaemic metabolic alkalosis2. We describe a 9½-year-old boy with Bartter's syndrome and severe retinopathy whose features may be those of a previously unrecognized disorder.

Bartter's syndrome: the unsolved puzzle

Bartter's syndrome is a congenital abnormality characterized by metabolic alkalosis [corrected], hyperreninemic hyperaldosteronism, and hypokalemia. Most patients present early in life with symptoms such as muscle weakness and polyuria, which may be attributed to potassium depletion. Despite the hyperaldosteronism, the patients tend to be normotensive, which is at least partially explained by vascular hyporesponsiveness to pressor hormones. Numerous studies have documented increased renal excretion of prostaglandins. Several different patterns of aberrant renal ion transport have been observed in patients with the syndrome, suggesting that it actually may represent a family of related but distinct tubular disorders. Therapeutic approaches to Bartter's syndrome include potassium supplementation, prostaglandin synthesis inhibitors (nonsteroidal anti-inflammatory agents), aldosterone antagonists, and converting enzyme inhibitors. During the first two decades following its initial description, Bartter's syndrome was the focus of widespread interest, based on the likelihood that its investigation might provide insight into the normal functioning of the renin-angiotensin-aldosterone and prostanoid hormone systems. During the past decade, however, little additional progress has been made in Bartter's syndrome, and its patho-physiology remains poorly understood.

Possible discrimination of Gitelman's syndrome from Bartter's syndrome by renal clearance study: report of two cases

We observed two patients who had hypokalemic metabolic alkalosis as well as hypomagnesemia and hypocalciuria with elevated serum renin levels. In renal clearance studies in our patients using furosemide or thiazide, urine volume and chloride clearance (CCI) were increased after furosemide administration but not after thiazide administration. Furthermore, the distal fractional chloride reabsorption [CH2O/(CH2O + CCI)] was dramatically decreased by furosemide administration in our patients, whereas thiazide had little effect on it, suggesting the presence of a defect in the distal tubule rather than in the thick ascending loop of Henle. These findings are compatible with the concept of Gitelman's syndrome, a variant form of Bartter's syndrome.

Genetic heterogeneity in tubular hypomagnesemia-hypokalemia with hypocalcuria (Gitelman's syndrome)

To better clarify the genetic inheritance of primary tubular hypomagnesemia-hypokalemia with hypocalciuria, or Gitelman's syndrome (GS), we studied eight families (10 patients aged 11 to 22 years; 16 parents; 9 siblings) in which at least one offspring had GS (plasma magnesium < 0.65 mmol/liter; plasma potassium < 3.6 mmol/liter; high magnesium and potassium fractional excretions; molar urinary calcium/creatinine < 0.10). Two families each had two offspring of different sex with GS, who all had tetanic episodes and/or marked weakness during childhood or adolescence, whereas in three other families two mothers and three offspring presented GS and one father and two other offspring had hypomagnesemia and hypocalciuria but normal plasma potassium. The mean plasma magnesium and potassium levels of the patients of the first two families were significantly lower (P < 0.05) than those of the other three families. Intralymphocytic but not intraerythrocytic magnesium and potassium were significantly lower (P < 0.05) in patients compared to controls. We hypothesize that there are two different types of genetic transmission of GS, one autosomal recessive and one autosomal dominant with high phenotype variability. It seems that this genetic heterogeneity is associated with a different clinical expression with frequent tetanic episodes and lower plasma potassium and magnesium levels in the autosomal recessive form.

Diseases of renal adenosine triphosphatase

Most renal transport is a primary or secondary result of the action of one of three membrane bound ion translocating ATPase pumps. The proximal tubule mechanisms for the reabsorption of salt, volume, organic compounds, phosphate, and most bicarbonate reabsorption depend upon the generation and maintenance of a low intracellular sodium concentration by the basolateral membrane Na-K-ATPase pump. The reabsorption of fluid and salt in the loop of Henle is similarly dependent on the energy provided by Na-K-ATPase activity. Some proximal tubule bicarbonate reabsorption and all distal nephron proton excretion is a product of one of two proton translocating ATPase pumps, either an electrogenic H-ATPase or an electroneutral H-K-ATPase. In this article, the authors review the biochemistry and physiology of pump activity and consider the pathophysiology of proximal and distal renal tubular acidosis, the Fanconi syndrome, and Bartter's syndrome as disorders of ATPase pump function.

A case of adult-onset Bartter's syndrome

Bartter's Syndrome is characterized by renal potassium wasting with hypokalemia, metabolic alkalosis, increased renin-angiotensin-aldosterone system, normal blood pressure, resistance to the pressor effects of angiotensin II and juxtaglomerular cell hyperplasia. Most of the cases have been noted in the pediatric age group and adult-onset cases are very rare. We report a case of adult-onset Bartter's syndrome.

Angiotensin II type 1 receptor gene abnormality in a patient with Bartter's syndrome

Administration of a selective angiotensin I type 1 receptor (AT1) antagonist in animals not only nullifies the vasopressor action of angiotensin II, but also induces chloriduria and kaliuria, juxtoglomerular apparatus (JGA) hypertrophy and hyperreninemia, features characteristic of human Bartter's syndrome. We, therefore, explored the possibility that Bartter's syndrome may involve an AT1 abnormality. Using a pair of AT1-specific oligonucleotide primers and two different DNA polymerases (Taq and Pfu), we amplified the approximately 1 kb AT1 coding region of genomic DNA isolated from leukocytes of five patients with Bartter's syndrome by PCR and analyzed the sequence of the product. While the sequence of all clones from four patients were identical to that already reported for the normal human AT1 DNA sequence, 50% of the clones from one patient with Bartter's syndrome were found to have A-->G transition at nucleotide 931 which causes an amino acid substitution (arg-->gly) on the carboxy-terminal cytosolic tail of AT1. This mutation was not found in DNA from 50 normal controls which were screened by restriction enzyme digestion pattern of the PCR products of this region. As PCR-amplified AT1 DNA clones from four other individuals with Bartter's syndrome did not display any abnormality in the coding region, the possibility exists that Bartter's syndrome consists of multiple disease entities, where an AT1 gene abnormality represents a specific subgroup of the syndrome and/or some abnormality includes mutations outside of the coding region.

Acute muscular paralysis in an adult with subclinical Bartter's syndrome associated with gentamicin administration

We report an adult case of asymptomatic Bartter's syndrome with the first presentation of hypokalemic paralysis triggered by gentamicin injection. Marked hypokalemia and hypomagnesemia associated with excessive kaliuresis and magnesiuria were found. Plasma renin activity and aldosterone concentration were high, but blood pressure was normal. Renal biopsy revealed hypercellularity of the renin-producing cell of the juxtaglomerular apparatus. Muscular paralysis subsided after potassium chloride supplementation. Hypokalemia was corrected with potassium and magnesium supplements and the use of diclofenac. To the best of our knowledge, there have been no reports of muscular paralysis associated with gentamicin in Bartter's syndrome.

Magnesium deficiency: pathophysiologic and clinical overview

Magnesium is an essential cation, involved in many enzymatic reactions, as a cofactor to adenosine triphosphatases. It is critical in energy-requiring metabolic processes, as well as protein synthesis and anaerobic phosphorylation. Serum Mg concentration is maintained within a narrow range by the kidney and small intestine since under conditions of Mg deprivation both organs increase their fractional absorption of Mg. If Mg depletion continues, the bone store contributes by exchanging part of its content with extracellular fluid (ECF). The serum Mg can be normal in the presence of intracellular Mg depletion, and the occurrence of a low level usually indicates significant Mg deficiency. Hypomagnesemia is frequently encountered in hospitalized patients and is seen most often in patients admitted to intensive care units. The detection of Mg deficiency can be increased by measuring Mg concentration in the urine or using the parenteral Mg load test. Hypomagnesemia may arise from various disorders of the gastrointestinal tract, conditions affecting Mg renal handling, or cellular redistribution of Mg. The gastrointestinal causes include the following: protein-calorie malnutrition, the intravenous administration of Mg-free fluids and total parenteral nutrition, chronic watery diarrhea and steatorrhea, short bowel syndrome, bowel fistula, continuous nasogastric suctioning, and, rarely, primary familial Mg malabsorption. The renal causes include Bartter's and Gitelman's syndrome, post obstructive diuresis, post acute tubular necrosis, renal transplantation, and interstitial nephropathy. Many therapeutic agents cause renal Mg wasting and subsequent deficiency. These include loop and thiazide diuretics, aminoglycosides, cisplatin, pentamidine, and foscarnet. Magnesium deficiency is seen frequently in alcoholics and diabetic patients, in whom a combination of factors contributes to its pathogenesis. Hypomagnesemia is known to produce a wide variety of clinical presentations, including neuromuscular irritability, cardiac arrhythmias, and increased sensitivity to digoxin. Refractory hypokalemia and hypocalcemia can be caused by concomitant hypomagnesemia and can be corrected with Mg therapy. The dose and route of administration of Mg in the treatment of hypomagnesemia is dictated by the clinical presentation, the degree of Mg deficiency, and the renal function.

Erythrocyte and mononuclear blood cell magnesium concentrations are normal in hypomagnesemic patients with chronic renal magnesium wasting

OBJECTIVE

The purpose of this study was to determine the plasma, erythrocyte, and mononuclear blood cell (MBC) magnesium concentrations in patients with chronic, severe hypomagnesemia due to a chronic magnesium-wasting tubulopathy.

METHODOLOGY

Six patients with Bartter's syndrome and five patients with magnesium-wasting tubulopathy were compared with normal subjects. We determined magnesium in plasma, erythrocytes, and MBCs.

RESULTS

Patients with chronic magnesium-wasting tubulopathy had a significantly lower plasma magnesium concentration than controls, but erythrocyte magnesium concentration and MBC magnesium concentration and content did not differ significantly between patients and controls.

CONCLUSION

Two disorders with chronic magnesium-wasting tubulopathies are associated with a low plasma magnesium concentration but normal erythrocyte and MBC magnesium.

Disorders of potassium homeostasis: an approach based on pathophysiology

Disorders of potassium (K+) homeostasis are frequently encountered in clinical medicine and may have serious sequelae, particularly cardiac arrhythmias. Since long-term K+ balance depends on regulation of renal excretion of K+, the focus of this paper is to provide a novel way to analyze the K+ excretory process at the bedside in a noninvasive fashion. A fundamental aim was to incorporate recent new advances in K+ physiology to the clinical analysis of K+ disorders. In so doing, we have tried to replace eponyms and largely descriptive terms with more specific, but hypothetical pathophysiologic diagnoses. The approach we used focuses on an assessment of the components of K+ excretion in vivo. If the rate of excretion of K+ differs from the "expected" value for the stimulus of hypokalemia or hyperkalemia, one should determine whether the fault is with the flow rate and/or the [K+] in the terminal cortical collecting duct. The former is influenced primarily by the rate of excretion of osmoles when antidiuretic hormone acts, whereas the [K+] in the cortical collecting duct is determined by factors that modulate rate of electrogenic reabsorption of Na+ in that segment and its conductance for K+. By examining the extracellular fluid (ECF) volume status, the plasma renin activity, and the renal response to the induction of ECF volume contraction, we attempted to deduce whether the change in electrogenic reabsorption of Na+ was due to an altered Na+ transport or apparent permeability to chloride in the cortical collecting duct. We believe that an approach which draws heavily on pathophysiology can be of practical use at the bedside and, in addition, indicate areas in which more research could be fruitful. To illustrate these points, two clinical cases with hypokalemia and two with hyperkalemia were analyzed. Nevertheless, it is important to emphasize that the approach provided is speculative.

Understanding and treating Bartter syndrome

Most of its clinical manifestations are the result of hypokalemia. The diagnosis is one of exclusion, mainly of surreptitious vomiting and diuretic abuse. The primary cause remains unknown but the most likely candidate is reduced sodium chloride reabsorption in the thick ascending limb of Henle's loop. Current therapy focuses on multiple agents to reduce massive potassium loss.

Bartter's syndrome in two generations of an Irish family

We report four cases of Bartter's syndrome in two consecutive generations of an Irish family. Diagnoses were made on the basis of characteristic clinical features, blood and urine biochemistry with additional evidence from renal biopsy in one case. The aetiology, treatment and inheritance of the syndrome are discussed.

Marked reduction of Tamm-Horsfall protein synthesis in hyperprostaglandin E-syndrome

Hyperprostaglandin E-syndrome (HPS), a recently described variant of Bartter's syndrome (BS), resembles BS in a number of symptoms but is distinct from BS in others. Similar to BS, HPS is characterized by congenital hypokalemic alkalosis, hypertrophy of the juxtaglomerular apparatus, hyperreninemia, secondary hyperaldosteronism, normal blood pressure and renal diabetes insipidus. Other than BS, HPS is constantly associated with chronic hypercalciuria and nephrocalcinosis as well as both renal and systemic PGE2 overproduction. Correction of most of the symptoms in HPS is achieved by permanent inhibition of prostaglandin synthesis with indomethacin. Among the causes leading to HPS, a selective damage of the distal tubule in HPS has been suggested. Therefore, synthesis of Tamm-Horsfall protein (THP), a glycoprotein exclusively produced in the thick ascending limb of the loop of Henle, was measured by ELISA in the urine of seven infant HPS patients (aged 3 to 8 years). Patients were investigated both under constant indomethacin treatment and after a one week period without indomethacin. Nine healthy children (aged 5 months to 10 years) served as controls. In controls mean daily THP excretion was 54.2 +/- 13.9 (median 46.0) mg/24 hr/1.73 m2 whereas in HPS, THP levels were strongly diminished. During withdrawal of indomethacin treatment, mean THP level was 12.7 +/- 10.1 (median 7.2) mg/24 hr/1.73 m2 and 10.3 +/- 10.1 (median 3.5) mg/24 hr/1.73 m2 under indomethacin treatment, respectively. THP excretion values both without indomethacin and under indomethacin treatment were significantly different from controls (P < or = 0.005); however, there was no significant difference between the THP levels during or after cessation of indomethacin treatment. Creatinine clearance in HPS patients was 75.1 +/- 15.9 (median 76.2) ml/min/1.73 m2 without indomethacin and 81.9 +/- 15.1 (median 83.0) ml/min/1.73 m2 under indomethacin treatment. Control values were not obtained. Comparative measurements of THP excretion in six classical BS-patients (aged 3 months to 17 years) revealed normal THP values in two individuals and intermediate levels in the others: the mean level of six BS patients was 30.8 +/- 13.5 (median 25.0) mg/24 hr/1.73 m2 and was thus significantly higher than in HPS both with and without indomethacin treatment (P < or = 0.05). Immunohistochemistry in renal biopsies of three of the HPS patients showed a strong reduction of cortical tubular THP immunoreactivity in two cases and a less pronounced reduction in the third. In situ hybridization using a THP-riboprobe in these three biopsies revealed significantly reduced or absent THP-mRNA levels.(ABSTRACT TRUNCATED AT 400 WORDS)

Oculocerebral hypopigmentation syndrome associated with Bartter syndrome

We describe a 20-year-old man with tyrosinase-negative oculocutaneous albinism, mental retardation, epilepsy, sensorineural deafness, ataxia, and Bartter syndrome. When combined, these neurocutaneous and renal findings form a previously unreported combination. The neurological and cutaneous manifestations of this case are distinctly different from those of the syndrome first reported by Cross et al. [1967]. The literature is reviewed and an attempt is made at classifying the oculocerebral hypopigmentation syndromes.