[Diagnosis and management of chronic kidney disease in children: Guidelines of the French Society of Pediatric Nephrology]

These guidelines are intended to assist physicians in the care of children with chronic kidney disease (CKD), defined in children as in adults, regardless of its cause. Often silent for a long time, CKD can evolve to chronic renal failure or end-stage renal disease. Its management aims at slowing disease progression and treating CKD complications as soon as they appear. The different aspects of pediatric CKD care are addressed in these guidelines (screening, treatment, monitoring, diet, quality of life) as proposed by the French Society of Pediatric Nephrology. Highly specialized care provided in the hospital setting by pediatric nephrologists is not detailed.

Toll-like receptor 3 expression and function in childhood idiopathic nephrotic syndrome

The efficacy of steroids and immunosuppressive treatments in idiopathic nephrotic syndrome (INS) hints at the implication of immune cells in the pathophysiology of the disease. Toll-like receptor (TLR) dysfunctions are involved in many kidney diseases of immune origin, but remain little described in INS. We investigated the expression and function of TLRs in peripheral blood mononuclear cells (PBMC) of INS children, including 28 in relapse, 23 in remission and 40 controls. No child had any sign of infection, but a higher Epstein-Barr virus viral load was measured in the PBMC of relapsing patients. TLR-3 expression was increased in B cells only during INS remission. There was a negative correlation between proteinuria and TLR-3 expression in total and the main subsets of PBMC from INS patients. The expression of TLR-8 was also increased in both CD4(+) T cells and B cells in INS remission. There was a negative correlation between proteinuria and TLR-8 expression in total PBMC, CD4(+) T cells and B cells of INS patients. Nevertheless, TLR-3 and TLR-8 expression was normalized in all PBMC subsets in an additional group of 15 INS patients in remission with B cell repletion after rituximab therapy. Paradoxically, interferon (IFN) regulatory factor 3 transactivation was increased in PBMC of all INS patients. In-vitro secretion of IFN-α and interleukin 6 were increased spontaneously in PBMC of INS remission patients, whereas PBMC from all INS patients displayed an impaired IFN-α secretion after TLR-3 stimulation. Thus, TLR-3 pathway dysfunctions may be closely involved in INS pathogenesis.

Comparison between valganciclovir and aciclovir/valaciclovir for CMV prophylaxis in pediatric renal transplantation

Prophylaxis has dramatically decreased the occurrence of cytomegalovirus (CMV) infection after renal transplantation. Optimal regimens of treatment remain controversial, especially in pediatric recipients. The aim of this study was to evaluate the effectiveness of valganciclovir (VGC) versus aciclovir/valaciclovir (ACV) in a pediatric renal transplant population. Data from 101 renal transplantations were retrospectively analyzed. Except those with R-/Dstatus, all patients received prophylaxis either with ACV, n = 39 or VGC, n = 38. Incidences of positive CMV antigenemia and disease, as well as the delay in relation to the prophylaxis, were collected during at least 12 months after the end of treatment. Positive CMV antigenemia was reported in 34 patients (ACV: 16, VGC: 16, no prophylaxis: 2). CMV disease occurred in 15 patients (ACV: 5; VGC: 8) (ns). For the majority of patients under VGC, positive CMV antigenemia occurred within the year following the withdrawal of prophylaxis (VGC: 14; ACV: 5, P <0.05), whereas it occurred during prophylaxis in 11 patients under ACV versus two under VGC (P <0.05). The over-all incidence of positive CMV antigenemia was similar between ACV and VGC prophylaxis. However, VGC was more efficient to prevent early CMV infection while patients treated with ACV had less CMV infection or disease after the end of the prophylaxis.

Evolution and prognosis value of intrarenal reflux

PURPOSE

The aim of this study was to evaluate the prognostic significance of intrarenal reflux (IRR) regarding urinary tract infection (UTI), renal scarring and spontaneous resolution after 3 years of follow up.

PATIENTS AND METHODS

33 patients (42 refluxing units) with IRR were compared to 27 children (44 refluxing units) with high-grade vesicoureteral reflux (VUR) without IRR (controls) matched for gender, age and VUR grade. All patients received antibiotic prophylaxis during observation and antireflux surgery was performed in children with recurrent UTI. DMSA scan was performed at study entry, and 18 and 36 months.

RESULTS

DMSA scores at entry showed a higher proportion of moderate and severe damage in the IRR group (25/42) compared to the control group (16/44) (Chi squared, P < 0.03). During follow up the incidence of UTI was similar in the two groups, as well as the stability of DMSA scintigraphy and the rate of spontaneous disappearance of the reflux. A similar proportion of patients underwent surgery (18/33 patients with IRR and 13/27 control patients; Chi squared, not significant).

CONCLUSIONS

Under medical management, the prognosis for IRR is not different from high-grade VUR without IRR. The presence of IRR does not justify more aggressive management than a high-grade VUR without IRR.

Successful anti-TNFalpha treatment in a child with posttransplant recurrent focal segmental glomerulosclerosis

Posttransplant recurrence of focal and segmental glomulosclerosis (FSGS) occurs in approximately 30% of patients, and remains after uncontrolled despite increased immunosuppression and plasma exchanges (PE) in approximately 30% of cases. New immunosuppressive drugs might then be warranted. We report the case of a 15-year-old boy with FSGS leading to end-stage renal disease (ESRD) who presented with an early posttransplant recurrence of disease. Reinforced immunosuppression and PE resulted in partial and transient disease control, but proteinuria significantly decreased with anti-TNFalpha treatment (infliximab then etanercep). This is the first case report of successful anti-TNFalpha treatment despite a constant high activity of FSGS, as demonstrated by relapse after discontinuation of anti-TNFalpha agents.

From humoral rejection to generalized thrombotic microangiopathy--role of acquired ADAMTS13 deficiency in a renal allograft recipient

A 9-year-old renal transplant recipient presented with elevated serum creatinine levels 4 years post-transplant renal biopsy revealed humoral rejection including lesions suggestive for thrombotic microangiopathy (TMA). He received methylprednisolone pulses followed by a normalization of serum creatinine. Two more steroid responsive acute rejection episodes occurred. Two months later he presented rapidly progressive life threatening symptoms including bilateral pyramidal syndrome and hemoptysis. Serum haptoglobin became undetectable at this time and platelet count decreased (70000/microl), suggesting TMA. Cerebral MRI revealed generalized ischemic white matter lesions. ADAMTS13 activity decreased to < 5%. Daily plasma exchanges (PE) resulted in immediate improvement. All attempts to discontinue PE were unsuccessful. Transplantectomy resulted in normalization of generalized symptoms, hemolysis and ADAMTS13 activity (110%). Multi-organ involvement has never been reported in acquired ADAMTS13 deficiency post-transplant. Rapid resolution after transplantectomy might suggest that renal TMA was responsible for acquired ADAMTS13 deficiency and thereby triggered the generalization of TMA lesions.

Rituximab therapy for childhood-onset systemic lupus erythematosus

OBJECTIVE

To describe the safety and efficacy of rituximab in the treatment of childhood-onset systemic lupus erythematosus (SLE).

STUDY DESIGN

We conducted a French multicenter retrospective study of childhood-onset SLE treated with rituximab.

RESULTS

Eleven girls with severe SLE, including 8 girls with class IV or V lupus nephritis, 2 girls with severe autoimmune cytopenia, and 1 girl with antiprothrombin antibody with severe hemorrhage, were treated with rituximab. The mean age at onset of rituximab treatment was 13.9 years. Patients received 2 to 12 intravenous infusions of rituximab (350-450 mg/m2/infusion), with corticosteroids. Six patients also received different standard immunosuppressive agents, including Cyclophosphamide (2 patients). Remission was achieved in 6 of 8 patients with lupus nephritis and in the 2 patients with autoimmune cytopenia. Steroid therapy was tapered in 5 patients who responded to treatment, and low-dose prednisone treatment was maintained in 1 patient. The mean follow-up period was 13.2 months (range, 6-26 months), and remission lasted in all who patients who responded to treatment, except 1 patient who was successfully retreated with a second course of rituximab. Anti-double-stranded DNA antibody levels decreased in 6 of 11 patients, and anticardiolipin antibody levels decreased in 3 of 4 patients. Severe adverse events developed in 5 patients. Effective depletion of peripheral blood B cells was observed in 7 of 8 patients who were examined, and this paralleled the remission.

CONCLUSION

Rituximab may be an effective co-therapy; however, further investigations are required because severe adverse events occurred in 45% of the patients in this study.

Initial presentation of childhood-onset systemic lupus erythematosus: a French multicenter study

OBJECTIVE

To describe the clinical and laboratory manifestations of childhood-onset systemic lupus erythematosus (SLE) at presentation.

STUDY DESIGN

This retrospective French multicenter study involved 155 patients in whom SLE developed before the age of 16 years. Mean patient age at onset was 11.5 +/- 2.5 years (range, 1.5-16 years). The female to male ratio was 4.5.

RESULTS

The most common initial manifestations were hematologic (72%), cutaneous (70%), musculoskeletal (64%), renal (50%), and fever (58%). Thirty-two percent of children had atypical symptoms, mainly including abdominal involvement in 26 patients, which lead to negative laparotomy results for presumed appendicitis. Severe renal, neurologic, hematologic, abdominal, cardiac, pulmonary, thrombotic, and/or cutaneous manifestations occurred within the first month after the diagnosis in 40% of patients. The mean erythrocyte sedimentation rate was 72 +/- 29 mm/h, and the mean C-reactive protein value 22 +/- 21 mg/L. Antinuclear antibodies an, anti-double stranded DNA antibodies, and low C3 or C4 level were retrieved in 97%, 93%, and 78 % of patients, respectively.

CONCLUSION

Initial manifestations of childhood-onset SLE are diverse and often severe. The diagnosis of SLE should be promptly considered in any febrile adolescent with unexplained organ involvement, especially when associated with an increased erythrocyte sedimentation rate.

[Immunity and immunosuppression in childhood idiopathic nephrotic syndrome]

Steroid sensitive idiopathic nephrotic syndrome is a T-cell disorder characterized by a functional renal impairment. Concluding a still relevant demonstration involving cellular immunity in the pathogenesis of the disease, R. Shalhoub in 1974 suggested a "special role for the thymus" based on the efficiency of steroids and alkylating agents, dramatic recoveries following measles, sensibility to bacterial infection due to a lack of cooperation between T and B cell and association to Hodgkin disease. As a matter of fact, the selected drugs based on medical empirism somehow enhance thymocytes apoptosis and negative selection of T cell, except cyclosporin. Steroids have been the first historical treatment of idiopathic nephrotic syndrome and have steadily been the first-line treatment for 50 years. Their unavoidable ability to induce rapid recovery of proteinuria and long-lasting or definite remission are dependent to a strict compliance to treatment. Indications of steroids-sparing treatments are not that clearcut in patients with steroids intoxication. Objectively, efficiency of levamisole and cyclophosphamide are much more limited than previously reported and cyclosporin nephrotoxicity might severely impair renal function following long-lasting treatment as well as it may paradoxically increase the activity of the disease. An alternate strategy to those currently adopted would use cyclosporin as the first-line steroids-sparing treatment during a very limited period, awaiting favourable ageing of patients and natural dampening activity of the disease to a full efficiency of alkylating agents. Compared to cyclophosphamide and cyclosporin, the relative safety of levamisole is encouraging to a more frequent uses. Its association to a full dose of prednisone in the treatment of the inaugural episode should be investigated. According to the limitations of those therapies, emerging drugs as mycophenolate might be worthwhile in the treatment of nephrotic patients.

Lupus érythémateux disséminé chez l'enfant : recommandations concernant les examens à effectuer lors de l'évaluation initiale et du suivi

Childhood-onset systemic lupus erythematosus (SLE) is often severe and has a serious long-term morbidity. Pediatric guidelines about its management do not exist. The French study group of childhood-onset SLE proposes recommendations about the investigation which are needed at diagnosis and during follow-up of SLE, in order to adjust the treatment according to the severity of the disease and to avoid unnecessary investigations.

[Cellular and molecular mechanisms of sodium pump activation in experimental models of nephrotic syndrome]

Edema represent an abnormal expansion of the intersTitial compartment which belong to the extracellular volume. This interstitial expansion is linked to the accumulation of sodium in the extracellular volume due to an imbalance between sodium intake and urinary sodium output. The stimulation of tubular sodium reabsorption is located in the collecting duct where a stimulation of sodium pump hydrolytic activity has been evidenced. The excess of sodium pump hydrolytic activity is associated with an overexpression of the alpha subunit of the sodium pump at the cell surface and a transcriptional induction of alpha and beta sub-units mRNAs. This overexpression is synchronized with the decrease of the final urinary sodium excretion, the positivation of sodium balance and the period of ascites formation.

[Childhood-onset systemic lupus erythematosus]

Systemic Lupus Erythematosus (SLE) remains a challenging autoimmune disease in term of etiology, pathogenesis and treatment. It is estimated that 10-17% of lupus patients present before the age of 16. SLE in children appears to have more severe organ involvement than in adults. The outcome of childhood SLE has improved during the last decade, but the morbidity remains high.

[Urinary antimicrobial prophylaxis]

Antibiotics are usually used to prevent childhood recurrent urinary tract infections: cystitis or pyelonephritis. The mechanism of action of these antibiotics, although imperfectly known, seems to be double: the antibiotic acts by its bactericidal effect, but also probably for minimal concentrations by reducing adhesion capability of bacteria to the urothelium. The most commonly used molecules are cotrimoxazole, trimethoprime, pivmecillinam, cefaclor and nalidixic acid. However all have not been studied rigorously as for their prophylactic capacity, and in particular very little is known for patients presenting with vesico-ureteral reflux.

[Primary molecular changes and secondary biological problems in Bartter and Gitelman syndrome]

Bartter syndrome and Gitelman syndrome are primary hereditary diseases characterized by hypokaliemia, alkalosis, hypertrophy of the juxtaglomerular complex with secondary hyperaldoteronism and normal blood pressure. They result from molecular disorders leading to a defect of sodium reabsorption in respectively the Henle's loop and the distal convoluted tubule. Biological adaptations of downstream tubular segments, i.e. distal convoluted tubule and collecting duct, are responsible for hypokaliemia, alkalosis, renin-aldosterone activation, prostaglandins hypersecretion and dysregulation of the urinary excretion of calcium and magnesium, illustrating the close integration of the regulation of different solutes in the distal tubular structures.

Successful plasma therapy in hemolytic uremic syndrome with factor H deficiency

A patient with homozygous factor H deficiency presented with hemolytic uremic syndrome (HUS) at the age of 7 months. After a 2-year period of stability, renal failure and erythrocyte fragmentation recurred between the age of 3 and 4 years. Fresh frozen plasma infusions allowed renal function to be improved and erythrocyte fragmentation to be stopped. Withdrawal of plasma therapy led to a relapse of the biological signs of HUS.

Prognosis of Streptococcus pneumoniae-induced hemolytic uremic syndrome

Streptococcus pneumoniae-induced hemolytic uremic syndrome (HUS) is known to be a severe acute disease leading to death in one-third of cases, but data regarding the long-term follow-up are lacking. A new series of 11 patients with Streptococcus pneumoniae-induced HUS associated with meningitis and pneumonia constituted a multi-center review. Among 9 patients with a severe acute infectious disease, 3 died from meningitis and 1 from neurological sequelae after a partial recovery of renal function. The mean duration of dialysis was 32 days in patients with acute renal failure who survived the acute infectious period. Cortical necrosis was documented in five of six kidney specimens. Among the 7 surviving patients, 5 developed end-stage renal failure 4-17 years later.

Cyclic AMP increases cell surface expression of functional Na,K-ATPase units in mammalian cortical collecting duct principal cells

Cyclic AMP (cAMP) stimulates the transport of Na(+) and Na,K-ATPase activity in the renal cortical collecting duct (CCD). The aim of this study was to investigate the mechanism whereby cAMP stimulates the Na,K-ATPase activity in microdissected rat CCDs and cultured mouse mpkCCD(c14) collecting duct cells. db-cAMP (10(-3) M) stimulated by 2-fold the activity of Na,K-ATPase from rat CCDs as well as the ouabain-sensitive component of (86)Rb(+) uptake by rat CCDs (1.7-fold) and cultured mouse CCD cells (1.5-fold). Pretreatment of rat CCDs with saponin increased the total Na,K-ATPase activity without further stimulation by db-cAMP. Western blotting performed after a biotinylation procedure revealed that db-cAMP increased the amount of Na,K-ATPase at the cell surface in both intact rat CCDs (1.7-fold) and cultured cells (1.3-fold), and that this increase was not related to changes in Na,K-ATPase internalization. Brefeldin A and low temperature (20 degrees C) prevented both the db-cAMP-dependent increase in cell surface expression and activity of Na,K-ATPase in both intact rat CCDs and cultured cells. Pretreatment with the intracellular Ca(2+) chelator bis-(o-aminophenoxy)-N,N,N',N'-tetraacetic acid also blunted the increment in cell surface expression and activity of Na,K-ATPase caused by db-cAMP. In conclusion, these results strongly suggest that the cAMP-dependent stimulation of Na,K-ATPase activity in CCD results from the translocation of active pump units from an intracellular compartment to the plasma membrane.

[Molecular mechanisms of idiopathic nephrotic syndrome]

Steroid-sensitive idiopathic nephrotic syndrome is a T-cell disorder associated with a functional renal impairment. The molecular mechanisms leading from the stimulation of the immune system to the clinical expression of the renal disease can be analyzed according to five biological events: 1) a Th2 activation of T-cells by interleukin-13; 2) a yet unidentified glomerular permeability factor from immune origin; 3) a molecular disorientation of slit diaphragms or glomerular basement membrane responsible for proteinuria; 4) a podocyte cytoskeleton rearrangement responsible for foot process effacement; and 5) renal avidity for sodium and edema formation resulting from a primary stimulation of tubular Na,K-ATPase and an increase of endothelial permeability.

Cellular adaptation of the mouse cortical thick ascending limb of Henle's loop (CTAL) to dietary magnesium restriction: enhanced transepithelial Mg2+ and Ca2+ transport

Mice aged 4 or 8 weeks were fed with a low-Mg2+ diet for 1, 2, 3 or 4 days. After 1 day of diet, the urinary excretion of Mg2+ and Ca2+ was strongly reduced in both animal groups (4 and 8 weeks), accompanied by a significant fall in plasma Mg2+ concentration and an increase in urinary volume. This profile persisted after 2, 3 or 4 days of dietary Mg2+ restriction. After 1 day of diet, transepithelial ion net fluxes of Na+, Cl-, Ca2+ and Mg2+ (JNa' JCI, JCl, JMg) measured in vitro from isolated perfused cortical thick ascending limbs (CTALs) of these animals remained unchanged. After 2 days of diet, measurements of J(Ca) and J(Mg) in isolated perfused CTALs showed that transepithelial Mg2+ and Ca2+ reabsorption were enhanced in CTALs from Mg(2+)-depleted, 8-week-old animals, whereas transepithelial Mg2+ and Ca2+ transport were not altered in 4-week-old mice. JNa and JCl and the transepithelial potential (PDte) were not modified in CTALs from either animal group. Our results suggest that a low-Mg2+ diet leads to urinary retention of Mg2+ and Ca2+ which is most likely due to increased Mg2+ and Ca2+ transport in the CTAL. Furthermore, in response to dietary Mg2+ restriction, the reabsorption of divalent cations in the CTAL of adult, but not of young, mice undergoes cellular adaptation.

[Renal K-ATPases: structure, function and dysfunction]

Na,K-ATPase and H,K-ATPase consist of two transmembrane proteins, the larger of which (catalytic subunit) exchanges extracellular K+ against intracellular Na+ or proton, at the expense of ATP hydrolysis. Cloning of four isoforms of Na,K-ATPase and two isoforms of H,K-ATPase has provided a molecular basis to the functional heterogeneity of these ATPases. Besides its house keeping functions, renal Na,K-ATPase energizes most solute and water transports along the whole nephron. For this purpose, it utilizes about 80% of renal metabolic energy. H,K-ATPase, which is restricted to the renal collecting duct, has a more limited role: it energizes K+ reabsorption during hypokalemia and, along with H-ATPase, participates to acid/base homeostasis. Dysregulation of tubular Na,K-ATPase and H,K-ATPase are involved in physiopathological alterations. For examples, results are presented which show the relationships that exist between a) Na+ retention during experimental nephrotic syndrome and stimulation of collecting duct Na,K-ATPase, and b) kaliuretic effect of loop diuretics and inhibition of collecting duct H,K-ATPase.

[The biochemical and hematological assessment of iron metabolism]

Despite the progress in the knowledge of iron metabolism, its precise assessment remains uneasy. Serum ferritin assesses the extent of storage iron. Serum iron and the percentage of transferrin saturation evaluate the tissues' iron supply. But these parameters are indirect measurements and they do not reflect marrow iron supply. Serum transferrin receptors, red cell ferritin and red cell zinc protoporphyrin are good indicators of this iron supply to the erythroid marrow for erythropoiesis. Since the introduction of recombinant human erythropoietin, it has become apparent that an adequate iron supply to the bone marrow is essential for a satisfactory hematopoietic response. In some cases, despite a high baseline ferritin, iron may not be sufficiently released from reserves in the bone marrow, resulting in a functional iron deficiency. The percentage of hypochromic red cells and reticulocyte haemoglobin content tends to reflect direct marrow iron status.

Large deletion of the 5' end of the ROMK1 gene causes antenatal Bartter syndrome

Mutations in exon 5 of the ROMK1 gene (KCNJ1) have recently been observed in antenatal Bartter syndrome patients. This study describes a homozygous deletion removing KCNJ1 exons 1 and 2 observed in a consanguineous family with antenatal Bartter syndrome. Absence of the untranslated exon 1 led to the deletion of transcription elements located in this exon that may cause the disease. Deletion of exon 1 transcription elements should lead to the absence of hROMK2-K5 transcripts, whereas hROMK1 transcripts should normally be transcripted. Consequently, probably only hROMK2-K5 transcripts are expressed in the medullary thick ascending limb of Henle.