Prenatal and postnatal management of hyperprostaglandin E syndrome after genetic diagnosis from amniocytes

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

Background

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

Case

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

Conclusion

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

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.

Transient hyponatremia of prematurity caused by mild Bartter syndrome type II: a case report

BACKGROUND

Bartter syndrome subtypes are a group of rare renal tubular diseases characterized by impaired salt reabsorption in the tubule, specifically the thick ascending limb of Henle's loop. Clinically, they are characterized by the association of hypokalemic metabolic alkalosis, hypercalciuria, nephrocalcinosis, increased levels of plasma renin and aldosterone, low blood pressure and vascular resistance to angiotensin II. Bartter syndrome type II is caused by mutations in the renal outer medullary potassium channel (ROMK) gene (KCNJ1), can present in the newborn period and typically requires lifelong therapy.

CASE PRESENTATION

We describe a case of a prematurely born female infant presenting with antenatal polyhydramnios, and postnatal dehydration and hyponatremia. After 7 weeks of sodium supplementation, the patient demonstrated complete resolution of her hyponatremia and developed only transient metabolic alkalosis at 2 months of age but continues to be polyuric and exhibits hypercalciuria, without development of nephrocalcinosis. She was found to have two pathogenic variants in the KCNJ1 gene: a frameshift deletion, p.Glu334Glyfs*35 and a missense variant, p. Pro110Leu. While many features of classic ROMK mutations have resolved, the child does have Bartter syndrome type II and needs prolonged pediatric nephrology follow-up.

CONCLUSION

Transient neonatal hyponatremia warrants a multi-system workup and genetic variants of KCNJ1 should be considered.

Salt-Losing Tubulopathies in Children: What's New, What's Controversial?

Renal tubulopathies provide insights into the inner workings of the kidney, yet also pose therapeutic challenges. Because of the central nature of sodium in tubular transport physiology, disorders of sodium handling may affect virtually all aspects of the homeostatic functions of the kidney. Yet, owing to the rarity of these disorders, little clinical evidence regarding treatment exists. Consequently, treatment can vary widely between individual physicians and centers and is based mainly on understanding of renal physiology, reported clinical observations, and individual experiences. Salt-losing tubulopathies can affect all tubular segments, from the proximal tubule to the collecting duct. But the more frequently observed disorders are Bartter and Gitelman syndrome, which affect salt transport in the thick ascending limb of Henle's loop and/or the distal convoluted tubule, and these disorders generate the greatest controversies regarding management. Here, we review clinical and molecular aspects of salt-losing tubulopathies and discuss novel insights provided mainly by genetic investigations and retrospective clinical reviews. Additionally, we discuss controversial topics in the management of these disorders to highlight areas of importance for future clinical trials. International collaboration will be required to perform clinical studies to inform the treatment of these rare disorders.

The Drosophila melanogaster model for Cornelia de Lange syndrome: Implications for etiology and therapeutics

Discovery of genetic alterations that cause human birth defects provide key opportunities to improve the diagnosis, treatment, and family counseling. Frequently, however, these opportunities are limited by the lack of knowledge about the normal functions of the affected genes. In many cases, there is more information about the gene's orthologs in model organisms, including Drosophila melanogaster. Despite almost a billion years of evolutionary divergence, over three-quarters of genes linked to human diseases have Drosophila homologs. With a short generation time, a twenty-fold smaller genome, and unique genetic tools, the conserved functions of genes are often more easily elucidated in Drosophila than in other organisms. Here we present how this applies to Cornelia de Lange syndrome, as a model for how Drosophila can be used to increase understanding of genetic syndromes caused by mutations with broad effects on gene transcription and exploited to develop novel therapies. © 2016 Wiley Periodicals, Inc.

Neonates with Bartter syndrome have enormous fluid and sodium requirements

AIM

Managing neonatal Bartter syndrome by achieving adequate weight gain is challenging. We assessed the correlation between weight gain in neonatal Bartter syndrome and the introduction of fluid and sodium supplementations and indomethacin during the first 4 weeks of life.

METHODS

Daily fluid and electrolytes requirements were analysed using linear regression and Spearman correlation coefficients. The weight gain coefficient was calculated as daily weight gain after physiological neonatal weight loss.

RESULTS

We studied seven infants. The highest weight gain coefficients occurred between weeks two and four in the five neonates who either received prompt amounts of fluid (maximum 810 mL/kg/day) and sodium (maximum 70 mmol/kg/day) or were treated with indomethacin. For the two patients with the highest weight gain coefficient, water and sodium supplementations were decreased in weeks two to four leading to a significant negative Spearman correlation between weight gain and fluid supplements (r = -0.55 and -0.68) and weight gain and sodium supplementations (r = -0.96 and -0.72). The two patients with the lowest weight gain coefficient had positive Spearman correlation coefficients between weight gain and fluid and sodium supplementations.

CONCLUSION

Infants with neonatal Bartter syndrome required rapid and enormous fluid and sodium supplementations or the early introduction of indomethacin treatment to achieve adequate weight gain during the early postnatal period.

Identification of the Conformational transition pathway in PIP2 Opening Kir Channels

The gating of Kir channels depends critically on phosphatidylinositol 4,5-bisphosphate (PIP2), but the detailed mechanism by which PIP2 regulates Kir channels remains obscure. Here, we performed a series of Targeted molecular dynamics simulations on the full-length Kir2.1 channel and, for the first time, were able to achieve the transition from the closed to the open state. Our data show that with the upward motion of the cytoplasmic domain (CTD) the structure of the C-Linker changes from a loop to a helix. The twisting of the C-linker triggers the rotation of the CTD, which induces a small downward movement of the CTD and an upward motion of the slide helix toward the membrane that pulls the inner helix gate open. At the same time, the rotation of the CTD breaks the interaction between the CD- and G-loops thus releasing the G-loop. The G-loop then bounces away from the CD-loop, which leads to the opening of the G-loop gate and the full opening of the pore. We identified a series of interaction networks, between the N-terminus, CD loop, C linker and G loop one by one, which exquisitely regulates the global conformational changes during the opening of Kir channels by PIP2.

Electrolyte disorders

Electrolyte disorders can result in life-threatening complications. The kidneys are tasked with maintaining electrolyte homoeostasis, yet the low glomerular filtration rate of neonatal kidneys, tubular immaturity, and high extrarenal fluid losses contribute to increased occurrence of electrolyte disorders in neonates. Understanding the physiologic basis of renal electrolyte handling is crucial in identifying underlying causes and initiation of proper treatment. This article reviews key aspects of renal physiology, the diagnostic workup of disorders of plasma sodium and potassium, and the appropriate treatment, in addition to inherited disorders associated with neonatal electrolyte disturbances that illuminate the physiology of renal electrolyte handling.

Postnatal regulation of 15-hydroxyprostaglandin dehydrogenase in the rat kidney

Cyclooxygenase 2 (COX-2) has an established role in postnatal kidney development. 15-Hydroxyprostaglandin dehydrogenase (15-PGDH) is recently identified as an endogenous inhibitor of COX-2, limiting the production of COX-2-derived prostanoids in several pathological conditions. The present study was undertaken to examine the regulation of renal 15-PGDH expression during postnatal kidney development in rats compared with COX-2. qRT-PCR and immunoblotting demonstrated that 15-PGDH mRNA and protein in the kidney were present in neonates, peaked in the second postnatal week, and then declined sharply to very low level in adulthood. Immunostaining demonstrated that at the second postnatal week, renal 15-PGDH protein was predominantly found in the proximal tubules stained positive for Na/H exchanger 3 and brush borders (periodic acid-Schiff), whereas COX-2 protein was restricted to macular densa and adjacent thick ascending limbs. Interestingly, in the fourth postnatal week, 15-PGDH protein was redistributed to thick ascending limbs stained positive for the Na-K-2Cl cotransporter. After 6 wk of age, 15-PGDH protein was found in the granules in subsets of the proximal tubules. Overall, these results support a possibility that 15-PGDH may regulate postnatal kidney development through interaction with COX-2.

Antenatal bartter syndrome: a review

Antenatal Bartter syndrome (ABS) is a rare autosomal recessive renal tubular disorder. The defective chloride transport in the loop of Henle leads to fetal polyuria resulting in severe hydramnios and premature delivery. Early onset, unexplained maternal polyhydramnios often challenges the treating obstetrician. Increasing polyhydramnios without apparent fetal or placental abnormalities should lead to the suspicion of this entity. Biochemical analysis of amniotic fluid is suggested as elevated chloride level is usually diagnostic. Awareness, early recognition, maternal treatment with indomethacin, and amniocentesis allow the pregnancy to continue. Affected neonates are usually born premature, have postnatal polyuria, vomiting, failure to thrive, hypercalciuria, and subsequently nephrocalcinosis. Hypokalemia, metabolic alkalosis, secondary hyperaldosteronism and hyperreninaemia are other characteristic features. Volume depletion due to excessive salt and water loss on long term stimulates renin-angiotensin-aldosterone system resulting in juxtaglomerular hyperplasia. Clinical features and electrolyte abnormalities may also depend on the subtype of the syndrome. Prenatal diagnosis and timely indomethacin administration prevent electrolyte imbalance, restitute normal growth, and improve activity. In this paper, authors present classification, pathophysiology, clinical manifestations, laboratory findings, complications, and prognosis of ABS.

Antenatal Bartter's syndrome with sensorineural deafness

Bartter's syndrome is a group of inherited, salt-losing tubulopathies presenting as metabolic alkalosis with normotensive hyperreninemia and hyperaldosteronism. We report here the first case of a neonate with bilateral, sensorineural deafness, a variant of antenatal Bartter's syndrome from an Indian community.

Prenatal pharmacotherapy for fetal anomalies: a 2011 update

Fetal therapy can be defined as any prenatal treatment administered to the mother with the primary indication to improve perinatal or long-term outcomes for the fetus or newborn. This review provides an update of the pharmacological therapies that are solely directed at the fetus with anomalies and outlines a future transcriptomic approach. Fetal anomalies targeted with prenatal pharmacotherapy are a heterogeneous group of structural, endocrine, and metabolic conditions, including congenital cystic adenomatoid malformation (CCAM), congenital adrenal hyperplasia, congenital heart block, fetal tachyarrhythmias, inborn errors of metabolism, fetal thyroid disorders, and polyhydramnios. To date, the majority of pharmacotherapies for fetal anomalies have been evaluated only in retrospective, uncontrolled studies. The way forward will be with an evidence-based approach to prenatal pharmacological interventions.

Antenatal Bartter syndrome: analysis of two cases with placental findings

The prenatal diagnosis of Bartter syndrome can be based on the high chloride level in the amniotic fluid. Microscopic examination of the placenta in untreated cases showed extensive mineralization in the chorionic villi in previous studies. Two cases were presented at 26-29 weeks of gestation with severe polyhydramnios. The mothers were treated with Indomethacin, KCl, and serial amniocentesis in order to reduce the amniotic fluid volume and prevent fetal hypokalemia. The microscopic examination of the placenta revealed focal calcification and acute atherosis in placental vessels. The treatment with Indomethacin in the antenatal period can prevent severe nephrocalcinosis.

Chronic renal failure in a boy with classic Bartter's syndrome due to a novel mutation in CLCNKB coding for the chloride channel

BACKGROUND

Progressive renal failure in patients with classic Bartter's syndrome (cBS) due to inactivating mutations in CLCNKB gene is extraordinarily rare.

DISCUSSION

We describe a 17-year-old Chinese boy who presented with progressive muscle weakness and renal failure. He was diagnosed as BS of unknown type at the age of 9 months and treated with indomethacin (2 mg/kg/day) and potassium chloride (KCl) supplementation (1.5 mEq/kg/day) for hypokalemia (2.5 mmol/l). At the age of 12 years, serum K+ was 3.0 mmol/l and creatinine reached 2.0 mg/dl. On admission, his blood pressure was normal but volume status was depleted. Urinalysis was essentially normal. Biochemical studies showed hypokalemia (K+ 2.4 mmol/l) with a high transtubular K+ gradient (TTKG) 9.6, metabolic alkalosis (HCO3- 28.4 mmol/l), normomagnesemia (2.0 mg/dl), severe renal failure (BUN 94 mg/dl, Cr 6.3 mg/dl), and hypocalciuria (urine calcium/creatinine ratio 0.02 mg/mg). Abdominal sonography revealed bilateral small size kidneys without nephrocalcinosis or renal stones. After the withdrawal of indomethacin with regular KCl and adequate fluid supplementation for 1 year, serum creatinine and K+ levels have been maintained at 4.0 mg/dl and 3.3 mmol/l, respectively. Direct sequencing of NKCC2, ROMK, ClC-Kb, and NCCT in this patient disclosed a novel homozygous missense mutation (GGG to GAG, G470E) in CLCNKB. This G470E mutation was not identified in 100 healthy Chinese subjects. Long-term therapy of non-steroidal anti-inflammatory drugs (NSAIDs), prolonged hypokalemia, chronic volume depletion, and underlying genetic variety may contribute to the deterioration of his renal function. The cautious use of NSAIDs, aggressive correction of hypokalemia, and avoidance of severe volume depletion may prevent the irreversible renal damage in patients with BS due to a Cl- channel defect.

Indomethacin-induced colon perforation in Bartter's syndrome

Bartter's syndrome (BS) is an inherited renal tubular disorder characterized by hypokalemia, hypochloremic metabolic alkalosis, and hyperaldosteronism with normal blood pressure. A 22-year-old woman was referred at 23 week of gestation. Polyhydramnios was detected and the chloride level of the amniotic fluid was high. The mother was treated with indomethacin from 26 to 31 week of gestation. The newborn was delivered at 34 week of gestation. At 8th day of life, indomethacin was also started for the baby. After three days, a colonic perforation developed. Indomethacin-induced colon perforation is uncommon in antenatal Bartter's syndrome. This patient indicates that administration of indomethacin in both antenatal and/or early postnatal period may be associated with colonic perforation.

An improved terminology and classification of Bartter-like syndromes

This Review outlines a terminology and classification of Bartter-like syndromes that is based on the underlying causes of these inherited salt-losing tubulopathies and is, therefore, more clinically relevant than the classical definition. Three major types of salt-losing tubulopathy can be defined: distal convoluted tubule dysfunction leading to hypokalemia (currently known as Gitelman or Bartter syndrome), the more-severe condition of polyuric loop dysfunction (often referred to as antenatal Bartter or hyperprostaglandin E syndrome), and the most-severe condition of combined loop and distal convoluted tubule dysfunction (antenatal Bartter or hyperprostaglandin E syndrome with sensorineural deafness). These three subtypes can each be further subdivided according to the identity of the defective ion transporter or channel: the sodium-chloride cotransporter NCCT or the chloride channel ClC-Kb in distal convoluted tubule dysfunction; the sodium-potassium-chloride cotransporter NKCC2 or the renal outer medullary potassium channel in loop dysfunction; and the chloride channels ClC-Ka and ClC-Kb or their beta-subunit Barttin in combined distal convoluted tubule and loop dysfunction. This new classification should help clinicians to better understand the pathophysiology of these syndromes and choose the most appropriate treatment for affected patients, while avoiding potentially harmful diagnostic and therapeutic approaches.

Inherited Renal Tubulopathies Associated With Metabolic Alkalosis: Effects on Blood Pressure

Inherited tubular disorders associated with metabolic alkalosis are caused by several gene mutations encoding different tubular transporters responsible for NaCl renal handling. Body volume and renin-angiotensin-aldosterone system status are determined by NaCl reabsorption in the distal nephron. Two common hallmarks in affected individuals: hypokalemia and normal / high blood pressure, support the differential diagnosis. Bartter's syndrome, characterized by hypokalemia and normal blood pressure, is a heterogenic disease caused by the loss of function of SLC12A1 (type 1), KCNJ1 (type 2), CLCNKB (type 3), or BSND genes (type 4). As a result, patients present with renal salt wasting and hypercalciuria. Gitelman's syndrome is caused by the loss of funcion of the SLC12A3 gene and may resemble Bartter's syndrome, though is associated with the very low urinary calcium. Liddle's syndrome, also with similar phenotype but with hypertension, is produced by the gain of function of the SNCC1B or SNCC1G genes, and must be distinguished from other entities of inherited hypertension such as Apparently Mineralocorticoid Excess, of glucocorticoid remediable hypertension.

Perinatal management of a preterm neonate affected by hyperprostaglandin E2 syndrome (HPS)

BACKGROUND

Neonates affected by hyperprostaglandin E(2) syndrome (HPS) present with severe polyuria. Both urinary losses as well as prostaglandin synthesis inhibitors may precipitate acute renal failure (ARF).

AIM

Our goal was to maintain euvolaemia by replacement of urinary losses.

PATIENT

Our patient was born prematurely with a family history typical of HPS. Urinary salt and water losses and PGE(2) excretion were determined in 2- to 4-h intervals. Salt and water were replaced accordingly.

RESULTS

Within the first 48 h, urinary losses and PGE(2) increased continuously to 50 ml/kg/h and 374 ng/h/1.73 m(2), respectively. Following exposure to 0.05-0.5 mg/kg/d indomethacin, urinary output decreased steadily to 10-15/ml/kg/h.

CONCLUSION

In euvolaemic preterm neonates with HPS and the need for excessive replacement of salt and water, inhibition of renal PGE(2) excretion with indomethacin effectively reduces polyuria and natriuresis without acutely compromising renal function.

Salt handling in the distal nephron: lessons learned from inherited human disorders

The molecular basis of inherited salt-losing tubular disorders with secondary hypokalemia has become much clearer in the past two decades. Two distinct segments along the nephron turned out to be affected, the thick ascending limb of Henle's loop and the distal convoluted tubule, accounting for two major clinical phenotypes, hyperprostaglandin E syndrome and Bartter-Gitelman syndrome. To date, inactivating mutations have been detected in six different genes encoding for proteins involved in renal transepithelial salt transport. Careful examination of genetically defined patients (“human knockouts”) allowed us to determine the individual role of a specific protein and its contribution to the overall process of renal salt reabsorption. The recent generation of several genetically engineered mouse models that are deficient in orthologous genes further enabled us to compare the human phenotype with the animal models, revealing some unexpected interspecies differences. As the first line treatment in hyperprostaglandin E syndrome includes cyclooxygenase inhibitors, we propose some hypotheses about the mysterious role of PGE2in the etiology of renal salt-losing disorders.

[Congenital hypomagnesemia]

MORE PRECISE IDENTIFICATION: The progress in molecular genetics has led to better understanding of primitive magnesium deficiency. Transporters of this cation have been identified in the intestines and kidneys. The majority of congential hypomanesemia phenotypes have been correlated with a defect in magnesium transport. The primary deficiency of intestinal absorption of magnesium is responsible for hypomagnesemia and subsequent hypocalcemia. DEPENDING ON THE MECHANISM: Magnesium absorption defects in Henle's loop induce hypomagnesemia with hypercalciuria and nephrocalcinosis, autosomal dominant hypocalcemia or Bartter syndrome. In isolated dominant hypomagnesemia and Gitelman syndrome, an abnormality in the distal convoluted tubule explains the primitive hypomagnesemia, through renal leaking. Conversely, the mechanisms of recessive isolated hypomagnesemia remains unknown. ORIENTING GENETIC DIAGNOSIS: In a context of primitive hypomagnesemia, the clinical and biological presentation will orient genetic research leading to correct diagnosis. However, there are many border-line phenotypes and the pheno-genotype correlation is still imperfect.

The role of cyclooxygenases and prostanoid receptorsin furosemide-like salt losing tubulopathy: the hyperprostaglandin E syndrome

Hyperprostaglandin E syndrome/antenatal Bartter syndrome is characterized by NaCl wasting and volume depletion, juxtaglomerula hypertrophy, hyperreninism and secondary hyperaldosteronism. Primary causes are mutations in the gene for Na-K-2Cl-cotransporter, NKCC2, or for potassium channel, ROMK, responsible for medullary NaCl malabsorption. Most intriguing aspect of the syndrome is the association with a massively increased renal prostaglandin production which contributes substantially to the clinical picture of the patients. Therefore the term hyperprostaglandin E syndrome has been introduced. It is unclear how prostaglandins aggravate the NaCl transport deficiency. Aspects to prostaglandin synthesis and receptor-mediated function within the kidney in patients suffering from hyperprostaglandin E syndrome/antenatal Bartter syndrome will be discussed.

Bartter's and Gitelman's syndromes: from gene to clinic

Bartter's and Gitelman's syndromes are characterized by hypokalemia, normal to low blood pressure and hypochloremic metabolic alkalosis. Recently, investigators have been able to demonstrate mutations of six genes encoding several renal tubular transporters and ion channels that can be held responsible for Bartter's and Gitelman's syndromes. Neonatal Bartter's syndrome is caused by mutations of NKCC2 or ROMK, classic Bartter's syndrome by mutations of ClC-Kb, Bartter's syndrome associated with sensorineural deafness is due to mutations of BSND, Gitelman's syndrome to mutations of NCCT and Bartter's syndrome associated with autosomal dominant hypocalcemia is linked to mutations of CASR. We review the pathophysiology of these syndromes in relation to their clinical presentation.

The neonatal variant of Bartter syndrome and deafness: preservation of renal function

BACKGROUND

A subtype of antenatal Bartter syndrome and sensorineural deafness (BSND) was originally described among families from southern Israel, and its gene (Barttin, OMIM #606412) has recently been identified. A report has suggested that these children develop chronic renal insufficiency during childhood attributable to chronic tubulointerstitial fibrosis and atrophy.

METHODS

Data from 13 infants with BSND, who were born during a 20-year period in our institution, were retrospectively analyzed.

RESULTS

All pregnancies were complicated by polyhydramnion and premature birth. All patients have sensorineural deafness, as well as hypokalemic metabolic alkalosis. Persistent hypercalciuria or nephrocalcinosis were absent in most children. All children have been treated with indomethacin (2 mg/kg/d) and potassium supplementation. The current average serum creatinine and calculated creatinine clearance from the older group (n = 8; mean age: 8.8 +/- 1.4 years) is 60.8 +/- 16.5 micro mol/L and 95 +/- 20 mL/min/1.73m(2), respectively. Kidney biopsies from two 7-year-old patients revealed mild focal tubulointerstitial fibrosis and minimal mesangial proliferation but no glomerulosclerosis.

CONCLUSIONS

Early renal function deterioration is not a uniform finding among children with BSND mutations.

Neonatal Bartter syndrome with unilateral multicystic dysplastic kidney disease

Neonatal Bartter syndrome is characterized by antenatal presentation with polyhydramnios. In this paper, we report a case of neonatal Bartter syndrome associated with unilateral multicystic dysplastic kidney disease. To our knowledge, this is the first case report of such an association.

Successful management of an extreme example of neonatal hyperprostaglandin-E syndrome (Bartter's syndrome) with the new cyclooxygenase-2 inhibitor rofecoxib

OBJECTIVE

To describe the successful treatment of an unusual case of severe neonatal Bartter's syndrome refractory to treatment with indomethacin.

DESIGN

Case report, clinical.

SETTING

Tertiary care intensive care unit.

PATIENTS

A patient with neonatal hyperprostaglandin-E syndrome and excessive requirements of intravenous (via central venous catheter) water and salt supplementation, failure to thrive, vomiting, and massive growth retardation, despite adequate treatment with indomethacin.

MAIN RESULT

Four weeks after induction of the new cyclooxygenase-2 inhibitor rofecoxib, the patient was well, on full enteral feeds, thriving, and had gained 600 g in weight. A lower supplementary potassium, magnesium, and sodium intake was required. Reinstitution of indomethacin therapy resulted in severe deterioration, despite high indomethacin doses; symptoms improved again after rofecoxib administration. No side effects have been seen thus far.

CONCLUSION

This report shows that in selected patients with a severe form of neonatal Bartter's syndrome, the new cyclooxygenase-2 inhibitor rofecoxib may control the clinical symptoms of hyperprostaglandin-E syndrome after ineffective indomethacin therapy.

Transient neonatal hyperkalemia in the antenatal (ROMK defective) Bartter syndrome

OBJECTIVE

Identification of neonatal hyperkalemia as a complication of Bartter syndrome (BS), a disorder usually characterized by hypokalemic metabolic alkalosis. Study design Case-series description of a group of 12 infants with mutations in the renal potassium channel ROMK, causing one of the antenatal variants of BS.

RESULTS

Prematurity, postnatal polyuria, and dehydration were seen in all cases. Plasma potassium was as high as 9.0 +/- 1.2 mmol/L and sodium as low as 124 +/- 3.5 mmol/L, appearing usually at day 3 of life and normalizing by the end of the first postnatal week. No hyperkalemia was found in 12 neonates with the variant of BS and deafness. The mean plasma potassium level during the first week of life among a group of very low-birth-weight infants with similar relative azotemia was 4.9 +/- 1 mmol/L (P <.001). The postneonatal period in the ROMK-defective children with BS was characterized by failure to thrive, hypercalciuria, nephrocalcinosis, and minimal-to-no hypokalemia.

CONCLUSIONS

Early postnatal hyperkalemia, sometimes severe, may complicate antenatal BS associated with ROMK mutations. Its association with hyponatremia and hyperreninemic hyperaldosteronism may erroneously suggest the diagnosis of pseudohypoaldosteronism type 1. The expression of ROMK in both the thick ascending limb and cortical collecting duct may explain this apparently tubular maturation phenomenon.

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.

Evaluation of long-term treatment with indomethacin in hereditary hypokalemic salt-losing tubulopathies

OBJECTIVE

Evaluation of the benefit/risk ratio of long-term treatment with indomethacin in salt-losing tubulopathies with special attention to renal function.

STUDY DESIGN

Twelve patients (median age, 14.9 years) had received indomethacin for a median of 13 years (median cumulative dose, 10.7 g/kg). Creatinine clearance, serum electrolyte levels, endocrine status, and excretion of prostaglandins and electrolytes were examined during indomethacin therapy and after its withdrawal. All patients underwent ultrasound-guided renal biopsy. For statistical evaluation, the Wilcoxon test and Pearson correlation coefficient were used.

RESULTS

After indomethacin withdrawal, the biochemical features of the tubulopathy reappeared. The median creatinine clearance rose from 67.4 to 96.5 mL/min/1.73 m(2) (P <.05) but remained subnormal in 4 patients. Ultrasonography elucidated medullary nephrocalcinosis in 8 patients. Renal tissue showed slight/moderate focal tubular atrophy and interstitial fibrosis in 8 patients. Comparison with biopsy specimens, obtained 11 to 14 years before study participation from 5 patients, revealed no progression. A correlation between fractional sodium and magnesium excretion and percentage of altered tubulointerstitial compartment was found (P <.001). The 4 patients with mutations in the gene of the inwardly rectifying adenosine triphosphate-regulated potassium channel (ROMK) had almost normal renal histologic findings and normal renal function.

CONCLUSION

Renal function and histology are unaffected by long-term indomethacin treatment.

Sodium transport deficiency and sodium balance in gene-targeted mice

Animals with induced or natural null mutations in renal NaCl and water transporter genes provide a powerful tool to study the physiological mechanisms that enable the kidney to optimize the match between glomerular filtration rate and tubular reabsorption. Deficiencies in the Na/H exchanger NHE3 and in the water channel aquaporin 1 (AQP1) cause reductions in proximal fluid absorption which are accompanied by proportionate decrements in glomerular filtration rate (GFR). Compensation of the transport defect by a reduction in filtered load is so efficient that clinically symptomatic Na losses are not observed in either NHE3 or AQP1 deficient animals. On the other hand, severe syndromes of salt wasting are caused by loss of function of the Na,K,2Cl-cotransporter (NKCC2) in the thick ascending limb, or of the epithelial Na channel (ENaC) the collecting duct indicating that the severity of Na dysregulation is unrelated to the basal absorption of NaCl in a given nephron segment. In these states, the increased delivery of Na to downstream segments is not monitored by a sensor linked to the site of filtrate formation. In the absence of adaptations in the filtered load intrarenal compensation of a circumscribed NaCl malabsorption by adjustment of NaCl transport in other nephron segments is sometimes insufficient, particularly in the immature kidney of the newborn.

Hypokalemic salt-losing tubulopathy with chronic renal failure and sensorineural deafness

OBJECTIVE

To characterize a rare inherited hypokalemic salt-losing tubulopathy with linkage to chromosome 1p31.

METHODS

We conducted a retrospective analysis of the clinical data for 7 patients in whom cosegregation of the disease with chromosome 1p31 had been demonstrated. In addition, in 1 kindred, prenatal diagnosis in the second child was established, allowing a prospective clinical evaluation.

RESULTS

Clinical presentation of the patients was homogeneous and included premature birth attributable to polyhydramnios, severe renal salt loss, normotensive hyperreninemia, hypokalemic alkalosis, and excessive hyperprostaglandin E-uria, which suggested the diagnosis of hyperprostaglandin E syndrome/antenatal Bartter syndrome. However, the response to indomethacin was only poor, accounting for a more severe variant of the disease. The patients invariably developed chronic renal failure. The majority had extreme growth retardation, and motor development was markedly delayed. In addition, all patients turned out to be deaf.

CONCLUSION

The hypokalemic salt-losing tubulopathy with chronic renal failure and sensorineural deafness represents not only genetically but also clinically a disease entity distinct from hyperprostaglandin E syndrome/antenatal Bartter syndrome. A pleiotropic effect of a single gene defect is most likely causative for syndromic hearing loss.

[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.

Treatment of childhood hypophosphatasia with nonsteroidal antiinflammatory drugs

Hypophosphatasia (HP) is an inborn error of metabolism that is characterized by reduced bone mineralization. The aim of this investigation was to evaluate treatment of incapacitating lower limb pain in patients with childhood HP using nonsteroidal antiinflammatory drugs (NSAID). All patients (seven boys; age 32 months to 16 years) presented with delayed walking, the typical waddling gait, muscular weakness of the lower limbs, and a limited walking distance. Six patients had severe diffuse lower limb pain following physical activity and were therefore treated with NSAID. The benefit of this treatment was evaluated clinically and by measurement of renally (PGE2) and systemically (PGE-M) derived prostaglandins (PG) in urine before and during therapy. After treatment with NSAID all six patients showed marked clinical improvement with reduced pain, increased muscle strength, and a normalized walking distance. Levels of PGE-M, which had been elevated in four patients prior to therapy, returned to normal. The use of NSAID in childhood HP should be considered as a possible therapeutic approach because the quality of life in these patients is markedly impaired by pain of the limbs. Elevated PG might play a role in the bone metabolism of HP patients.