Spironolactone: utilisation en pédiatrie

Clinical experience with spironolactone in pediatrics.

Buck ML.

Ann Pharmacother. 2005; 39:823-8.

BACKGROUND: In 2003, the Food and Drug Administration placedspironolactone on its list of drugs needing pediatric studies.OBJECTIVE: To describe the use of spironolactone in a large group ofchildren and evaluate its safety, focusing on its effects on potassium. METHODS: A prospective observational study was conducted. Patient demographic information was collected, as well as dosing regimens, useof other medications, and potassium concentrations. Patients were grouped by diagnosis. Comparisons were made with unpaired t-tests. RESULTS: One hundred consecutive patients were evaluated. The average age was 20.8 months and weight was 9.5 kg. Sixty-two patients had heart disease (HD), 29 had chronic lung disease (CLD), and 9 had other conditions. The initial dose was 1.8 +/- 0.7 mg/kg/day. Patients with CLD received a higher dose than those with HD (2 +/- 0.8 vs 1.7 +/- 0.5mg/kg/day; p = 0.04). Sixty-six patients received furosemide and 37 received thiazides (12 received both). The average potassium concentration after initiation was 4.3 +/- 0.8 mEq/L, with higher values in patients with CLD versus HD (4.7 +/- 0.7 vs 4.2 +/- 0.7 mEq/L; p =0.007). Twenty-six patients required potassium supplementation,including 16 with CLD and 8 with HD; no other adverse effects were noted. Average length of treatment was 16 days, with a length of stay of 38 days. Of the 92 patients surviving to discharge, 66 continued on spironolactone. CONCLUSIONS: This sample demonstrates that spironolactone is a common component of diuretic regimens in pediatric patients. The only adverse effects were alterations in potassium. Whilehyperkalemia was more common initially, hypokalemia was more frequent with long-term use. Potassium concentrations should be carefully monitored, particularly in children receiving multiple diuretics. Additional research is needed to define the pharmacokinetics and optimal dosing interval of spironolactone, as well as determine its long-term effects on potassium.

Quels examens radiologiques après une infection urinaire ?

The presence of vesicoureteric reflux does not identify a population at risk for renal scarring following a first urinary tract infection.
Moorthy I, Easty M, McHugh K, Ridout D, Biassoni L, Gordon I.

Arch Dis Child. 2005 Jul;90(7):733-6.
BACKGROUND: Childhood urinary tract infection (UTI) with or without vesicoureteric reflux (VUR) may predispose to renal scarring. There is no clear consensus in the literature regarding imaging following UTI in infancy. AIMS: To define the role of cystography following a first UTI in children aged under 1 year, when urinary tract ultrasonography (US) is normal. METHODS: Retrospective data collection of 108 children (216 renal units) aged under 1 year at the time of a bacteriologically proven UTI. All had a normal US and underwent both catheter cystogram and DMSA test. Sensitivity, specificity, likelihood ratios positive and negative, and diagnostic odds ratio were calculated for VUR on cystography versus scarring on DMSA. RESULTS: VUR was shown in 25 (11.6%) renal units. Scarring on DMSA was seen in 8 (3.7 %) kidneys. Only 16% of kidneys with VUR had associated scarring; 50% of scarred kidneys were not associated with VUR. The likelihood ratio positive was 4.95 (95% CI 2.22 to 11.05) and the likelihood ratio negative was 0.56 (95% CI 0.28 to 1.11). The diagnostic odds ratio was 8.9, suggesting that cystography provided little additional information. CONCLUSION: Since only 16% of children with VUR had an abnormal kidney, the presence of VUR does not identify a susceptible population with an abnormal kidney on DMSA. In the context of a normal ultrasound examination, cystography contributes little to the management of children under the age of 1 year with a UTI. In this context, a normal DMSA study reinforces the redundancy of cystography.


Urinary tract infection: is there a need for routine renal ultrasonography?

Zamir G, Sakran W, Horowitz Y, Koren A, Miron D.

Arch Dis Child. 2004;89:466-8.
AIMS: To assess the yield of routine renal ultrasound (RUS) in the management of young children hospitalised with first uncomplicated febrile urinary tract infection (UTI). METHODS: All children aged 0-5 years who had been hospitalised over a two year period with first uncomplicated febrile UTI in a medium size institutional regional medical centre were included. Children with known urinary abnormalities and/or who had been treated with antibacterial agents within seven days before admission were excluded. All included children underwent renal ultrasonography during hospitalisation and voiding cystouretrography (VCUG) within 2-6 months. The yield of RUS was measured by its ability to detect renal abnormalities, its sensitivity, specificity, and positive and negative predictive values for detecting vesicoureteral reflux (VUR), and by its impact on UTI management. RESULTS: Of 255 children that were included in the study, 33 children had mild to moderate renal pelvis dilatation on RUS suggesting VUR, of whom only nine had VUR on VCUG. On the other hand, in 36 children with VUR on VCUG the RUS was normal. The sensitivity, specificity, positive predictive value, and negative predictive value of abnormal RUS for detecting VUR were 17.7%, 87.6%, 23.5%, and 83.2% respectively. In none of the patients with abnormal RUS was a change in the management at or following hospitalisation needed. CONCLUSION: Results show that the yield of RUS to the management of children with first uncomplicated UTI is questionable.

Commentaires: Ces deux articles bousculent un peu les dogmes en posant la question de la pertinence de l'échographie et de la cystographie après un épisode d'infection urinaire chez le nourrisson. Ils font suite à un article de l'équipe d'Hoberman publié il y plus de deux ans dans le New England Journal of Medicine (voir ci-dessous) et qui concluait que l'échographie n'était pas inispensable ! Dans le premier papier les auteurs ont revu les cystographies (conventionnelle chez les garçons et isotopiques chez les filles) de tout les enfants âgés de 0 à 12 mois ayant eu une première infection urinaire. Sur les 108 nourrissons, 25 reflux était mis en evidence dont un seul de haut grade (l'écho était normale). Les corrélations entre la présence d'un RVU et celle de cicatrices ne sont pas bonnes. Les auteurs rappellent que des études récentes sur le long terme ont montré qu'il n'y avait pas de bonnes corrélations entre la présence de cicatrices et l'apparition d'une HTA. La vraie question reste donc celle de savoir s'il faut une antibioprophylaxie en cas de RVU de bas grade.

Dans le deuxième article qui est plus un commentaire de l'article d'Hoberman, l'analyse prospective de 255 cas (0 à 5 ans) montre qu'il n'y a pas de bonne corrélation entre l'écho et la cystographie en terme de prédiction de la présence d'un RVU. Chez les 14.1% des enfants ayant une écho anormale, l'attitude n'a pas été modifiée par le résultat de cet examen. Les auteurs arrivent aux mêmes conclusions qu'Hoberman: si l'écho anténatale est normale il n'est pas nécessaire de faire une écho après une infection urinaire. Encore faut-il être sur de la qualité de l'échographie anténatale ce qui n'est peut-être pas toujours si évident ...

Imaging studies after a first febrile urinary tract infection in young children.

Hoberman A, Charron M, Hickey RW, Baskin M, Kearney DH, Wald ER.
N Engl J Med. 2003;348:195-202.

BACKGROUND: Guidelines from the American Academy of Pediatrics recommend obtaining a voiding cystourethrogram and a renal ultrasonogram for young children after a first urinary tract infection; renal scanning with technetium-99m-labeled dimercaptosuccinic acid has also been endorsed by other authorities. We investigated whether imaging studies altered management or improved outcomes in young children with a first febrile urinary tract infection. METHODS: In a prospective trial involving 309 children (1 to 24 months old), an ultrasonogram and an initial renal scan were obtained within 72 hours after diagnosis, contrast voiding cystourethrography was performed one month later, and renal scanning was repeated six months later. RESULTS: The ultrasonographic results were normal in 88 percent of the children (272 of 309); the identified abnormalities did not modify management. Acute pyelonephritis was diagnosed in 61 percent of the children (190 of 309). Thirty-nine percent of the children who underwent cystourethrography (117 of 302) had vesicoureteral reflux; 96 percent of these children (112 of 117) had grade I, II, or III vesicoureteral reflux. Repeated scans were obtained for 89 percent of the children (275 of 309); renal scarring was noted in 9.5 percent of these children (26 of 275). CONCLUSIONS: An ultrasonogram performed at the time of acute illness is of limited value. A voiding cystourethrogram for the identification of reflux is useful only if antimicrobial prophylaxis is effective in reducing reinfections and renal scarring. Renal scans obtained at presentation identify children with acute pyelonephritis, and scans obtained six months later identify those with renal scarring. The routine performance of urinalysis, urine culture, or both during subsequent febrile illnesses in all children with a previous febrile urinary tract infection will probably obviate the need to obtain either early or late scans. Copyright 2003 Massachusetts Medical Society

Petit poids de naissance: dernières publications ...

Blood pressure in the small-for-gestational age newborn.

Strambi M, Vezzosi P, Buoni S, Berni S, Longini M.

Minerva Pediatr. 2004; 56:603-10.

AIM: The aim of the paper is to verify the existence of an inversecorrelation between birth weight and blood pressure (BP) in neonates,infants and adolescents. METHODS: BP was measured at 7 days, 3, 6, 9, 12months and 7-18 years in 432 subjects born at term at the Department ofPediatrics, Obstetrics and Reproductive Medicine, University of Siena;228 of these subjects were small for gestational age (SGA) and 204appropriate for gestational age (AGA). For small babies, BP was measuredwith a DYNAMAP oscillometer which provides digital visualisation ofsystolic, diastolic and mean arterial pressure and heart rate. In olderchildren, a mercury sphygmomanometer was used. Statistical analysis wascarried out with SPSS 8.01 software using the Kolmogorov-Smirnov testfor normality of populations. RESULTS: Statistical analysis did notreveal any significant differences between SGA and AGA subjects in thevarious age classes of the first 12 months of life. Significantcorrelation was found between 7 and 18 years with differences in thevarious age classes for systolic pressure. Subjects with normalbirthweight had lower systolic and diastolic BP. SGA males had higherrisk of high systolic and diastolic pressure, whereas SGA females wereonly at higher risk for elevated diastolic pressure. CONCLUSIONS: SGAsubjects should be monitored for BP and life-style between 7 and 18years to risk of cardiovascular disease.

Aortic wall thickness in newborns with intrauterine growth restriction.Skilton MR, Evans N, Griffiths KA, Harmer JA, Celermajer DS.

Lancet. 2005;365:1484-6

Much epidemiological evidence has linked low birthweight with late cardiovascular risk. We measured aortic wall thickness (a marker of early atherosclerosis) by ultrasonography in 25 newborn babies with intrauterine growth restriction and 25 with normal birthweight. Maximum aortic thicknesses were significantly higher in the babies with intrauterine growth restriction (810 microm [SD 113]) than in those without (743 microm [76], p=0.02), more so after adjustment for birthweight (300 microm/kg [45] vs 199 microm/kg [29], p<0.0001).>

Long-term renal follow-up of extremely low birth weight infants.

Rodriguez-Soriano J, Aguirre M, Oliveros R, Vallo A.

Pediatr Nephrol. 2005 May;20(5):579-84

There is evidence that low birth weight caused by intrauterine growth retardation adversely affects normal renal development. Very little information on this issue is available on children born very prematurely. This investigation examined clinical and functional renal parameters in 40 children (23 boys, 17 girls) ranging in age between 6.1 and 12.4 years and weighing less than 1000 g at birth. Results were compared to those obtained in 43 healthy children of similar age and gender. Study subjects were significantly smaller and thinner than control subjects (mean height SDS: -0.36 vs. +0.70; and mean BMI SDS: -0.56 vs. +1.18). Systolic, diastolic, and mean blood pressures did not differ from those of controls. Renal sonography revealed no abnormality, and mean percentiles for renal length and volume appeared normal. In comparison with controls, plasma creatinine concentration (0.62+/-0.1 vs. 0.53+/-0.1 mg/dl) and estimated creatinine clearance (117+/-17 vs. 131+/-17 ml min(-1) 1.73 m(-2)) differed significantly. No significant differences were observed in microalbuminuria values, but five study subjects (12.5%) presented values above the upper limit of normality. A defect in tubular phosphate transport was also evident: TmP/GFR (3.6+/-0.4 vs. 4.2+/-0.8 mg/dl) and TRP (83+/-5% vs. 90+/-4%) were significantly lower, and urinary P excretion, estimated by the ratio UP/UCr, was significantly higher (1.2+/-0.4 vs. 0.9+/-0.4 mg/mg) than controls. Urinary calcium excretion, estimated by the UCa/UCr ratio, was also significantly higher (0.15+/-0.07 vs. 0.12+/-0.09 mg/mg). These data clearly demonstrate that both GFR and tubular phosphate transport are significantly diminished in school-age children born with extreme prematurity, probably as a consequence of impaired postnatal nephrogenesis.

Commentaires: Trois publications récentes qui s'ajoutent à la littérature déjà prolixe depuis les premières publications de Barker à propos des conséquences sur la pression artérielle (PA) et la fonction rénale du retard de croissance intra-utérin.

L'étude italienne confirme ce qui a déjà été largement démontré à savoir que chez les enfants nés avec un petit poids de naissance (PPN) la PA est plus élevée à l'adolescence ou à l'âge adulte.

L'étude australienne publiée dans Lancet montre que l'épaisseur de l'intima aortique est plus importante chez les nouveaux-nés avec PPN. Ce marqueur précoce de la maladie athéromateuse est donc visible dès la naissance !

Enfin l'étude espagnole nous montre à partir du suivi de 40 enfants nés avec PN ... (suite ci-dessous)

RS

Syndrome de Gitelman: pourquoi la calciurie est basse ?

Enhanced passive Ca2+ reabsorption and reduced Mg2+ channel abundance explains thiazide-induced hypocalciuria and hypomagnesemia

Tom Nijenhuis1, Volker Vallon2, Annemiete W.C.M. van der Kemp1, Johannes Loffing3, Joost G.J. Hoenderop1 and René J.M. Bindels1

J. Clin. Invest. 115:1651-1658 (2005).

Thiazide diuretics enhance renal Na+ excretion by blocking the Na+-Cl– cotransporter (NCC), and mutations in NCC result in Gitelman syndrome. The mechanisms underlying the accompanying hypocalciuria and hypomagnesemia remain debated. Here, we show that enhanced passive Ca2+ transport in the proximal tubule rather than active Ca2+ transport in distal convolution explains thiazide-induced hypocalciuria. First, micropuncture experiments in mice demonstrated increased reabsorption of Na+ and Ca2+ in the proximal tubule during chronic hydrochlorothiazide (HCTZ) treatment, whereas Ca2+ reabsorption in distal convolution appeared unaffected. Second, HCTZ administration still induced hypocalciuria in transient receptor potential channel subfamily V, member 5–knockout (Trpv5-knockout) mice, in which active distal Ca2+ reabsorption is abolished due to inactivation of the epithelial Ca2+ channel Trpv5. Third, HCTZ upregulated the Na+/H+ exchanger, responsible for the majority of Na+ and, consequently, Ca2+ reabsorption in the proximal tubule, while the expression of proteins involved in active Ca2+ transport was unaltered. Fourth, experiments addressing the time-dependent effect of a single dose of HCTZ showed that the development of hypocalciuria parallels a compensatory increase in Na+ reabsorption secondary to an initial natriuresis. Hypomagnesemia developed during chronic HCTZ administration and in NCC-knockout mice, an animal model of Gitelman syndrome, accompanied by downregulation of the epithelial Mg2+ channel transient receptor potential channel subfamily M, member 6 (Trpm6). Thus, Trpm6 downregulation may represent a general mechanism involved in the pathogenesis of hypomagnesemia accompanying NCC inhibition or inactivation.

Commentaires : cet article propose une explication cohérente, basée sur des expériences solides avec modèles animaux, explication à l’hypocalciurie du syndrome de Gitelman : le syndrome de G est dû à une anomalie du cotransporteur Na Cl dans le tube contourné distal entraînant une perte de sel le plus souvent infraclinique et des signes biologiques nets : hypokaliémie et hypomagnésémie. Il paraissait logique (bien que le mécanisme ne soit pas compris) que l’hypocalciurie constamment associée soit due à une réabsorption accrue du calcium par un mécanisme en cascade situé également dans le tube distal. Cet article propose en fait que la réabsorption du calcium soit accrue dans le tube proximal. (vieille hypothèse classique de la diminution de la réabsorption du calcium dans le TP lorsque les volumes extra cellulaires sont diminués ), la réabsorption du calcium dans le tube distal étant normale.
Quant à l’hypomagnésémie, son mécanisme n’est pas encore très clair…….

Michèle Dechaux

Calcinose tumorale familiale : GALNT3 aussi !

Identification of a recurrent mutation in GALNT3 demonstrates that hyperostosis-hyperphosphatemia syndrome and familial tumoral calcinosis are allelic disorders.

Frishberg Y, Topaz O, Bergman R, Behar D, Fisher D, Gordon D, Richard G, Sprecher E.

J Mol Med. 2005;83:33-8.

Hyperphosphatemia-hyperostosis syndrome (HHS) is a rare autosomal recessive metabolic disorder characterized by elevated serum phosphate levels and repeated attacks of acute, painful swellings of the long bones with radiological evidence of periosteal reaction and cortical hyperostosis. HHS shares several clinical and metabolic features with hyperphosphatemic familial tumoral calcinosis (HFTC), which is caused by mutations in GALNT3 encoding a glycosyltransferase responsible for initiating O-glycosylation. To determine whether GALNT3 is involved in the pathogenesis of HHS we screened two unrelated Arab-Israeli HHS families for pathogenic mutations in this gene. All affected individuals harbored a homozygous splice site mutation (1524+1G-->A) in GALNT3. This mutation was previously described in a large Druze HFTC kindred and has been shown to alter GALNT3 expression and result in ppGalNAc-T3 deficiency. Genotype analysis of six microsatellite markers across the GALNT3 region on 2q24-q31 revealed that the HHS and HFTC families share a common haplotype spanning approximately 0.14 Mb. Our results demonstrate that HHS and HFTC are allelic disorders despite their phenotypic differences and suggest a common origin of the 1524+1G-->A mutation in the Middle East (founder effect). The heterogeneous phenotypic expression of the identified splice site mutation implies the existence of inherited or epigenetic modifying factors of importance in the regulation of ppGalNAc-T3 activity.

Commentaire : Un gène peut en cacher un second ! On apprend dans cet article que les mutations de GALNT3 donnent un tableau identique à celui entrainé par une mutation inhibitrice de FGF23 : la calcinose familiale tumorale... mais également les mutations de GALNT3 se retrouvent aussi dans le syndrome hyperostose hyperphosphatémie. GALNT3 codant pour une glycosyltransferase, et FGF23 étant glycosylé, l'hypothèse (non encore prouvée) reliant toutes ces anomalies est élégante et vient complêter les connaissances sur le métabolisme phosphocalcique.

Vincent Guigonis

La calcinose tumorale familiale: une mutation inactivatrice de FGF23

An FGF23 missense mutation causes familial tumoral calcinosis with hyperphosphatemia.

Benet-Pages A, Orlik P, Strom TM, Lorenz-Depiereux B.

Hum Mol Genet. 2005;14:385-90.

Familial tumoral calcinosis (FTC) is an autosomal recessive disorder characterized by ectopic calcifications and elevated serum phosphate levels. Recently, mutations in the GALNT3 gene have been described to cause FTC. The FTC phenotype is regarded as the metabolic mirror image of hypophosphatemic conditions, where causal mutations are known in genes FGF23 or PHEX. We investigated an individual with FTC who was negative for GALNT3 mutations. Sequencing revealed a homozygous missense mutation in the FGF23 gene (p.S71G) at an amino acid position which is conserved from fish to man. Wild-type FGF23 is secreted as intact protein and processed N-terminal and C-terminal fragments. Expression of the mutated protein in HEK293 cells showed that only the C-terminal fragment is secreted, whereas the intact protein is retained in the Golgi complex. In addition, determination of circulating FGF23 in the affected individual showed a marked increase in the C-terminal fragment. These results suggest that the FGF23 function is decreased by absent or extremely reduced secretion of intact FGF23. We conclude that FGF23 mutations in hypophosphatemic rickets and FTC have opposite effects on phosphate homeostasis.

Commentaire : Le premier d'une série d'articles décrivant le tableau clinique inverse du rachitisme hypophosphorémique secondaire à une mutation inhibitrice de FGF 23 : la calcinose tumorale familiale. A retenir pour les cas d'hyperphosphorémies inexpliquées.

Vincent Guigonis

Présentation initiale du lupus chez l'enfant: une étude multicentrique française

Initial presentation of childhood-onset systemic lupus erythematosus: a French multicenter study.
Bader-Meunier B, Armengaud JB, Haddad E, Salomon R, Deschenes G, Kone-Paut I, Leblanc T, Loirat C, Niaudet P, Piette JC, Prieur AM, Quartier P, Bouissou F, Foulard M, Leverger G, Lemelle I, Pilet P, Rodiere M, Sirvent N, Cochat P.

J Pediatr. 2005;146:648-53.

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.

Commentaires: Cette série rétrospective de 155 enfants atteints d'un lupus à partir d'un questionnaire envoyé aux cliniciens. 65 des 89 services contactés ont répondu dont 13 unités de néphrologie pédiatrique, 10 de rhumatologie, 8 de pédiatrie générale et 2 d'hématologie. Malgré les biais de recrutement inhérents à ce type de d'étude les résultast sont riches d'enseignements. On voit que dans 50% des cas il existe une atteinte rénale dès le début de la maladie, que les manifestations digestives ne sont pas si rares, qu'il existe des antécédents familiaux d'auto-immunité dans 26% des cas, que même dans les cas de lupus "incomplet" selon les critères de l'ACR il peut y avoir une atteinte rénale dans un tiers des cas dès le début, etc ... A lire !

Rappel: Les Archives Françaises de Pédiatrie ont publié l'année dernière un article récapitulant les examens utiles pour le bilan initial et pour le suivi des enfants atteints de lupus. Pratique.

Arch Pediatr. 2004 Aug;11(8):941-4.

RS

SIADH par mutations activatrices du récepteur de la vasopressine

Nephrogenic syndrome of inappropriate antidiuresis.

Feldman BJ, Rosenthal SM, Vargas GA, Fenwick RG, Huang EA, Matsuda-Abedini M, Lustig RH, Mathias RS, Portale AA, Miller WL, Gitelman SE.

N Engl J Med. 2005 May 5;352(18):1884-90.

The syndrome of inappropriate antidiuretic hormone secretion (SIADH) is a common cause of hyponatremia. We describe two infants whose clinical and laboratory evaluations were consistent with the presence of SIADH, yet who had undetectable arginine vasopressin (AVP) levels. We hypothesized that they had gain-of-function mutations in the V2 vasopressin receptor (V2R). DNA sequencing of each patient's V2R gene (AVPR2) identified missense mutations in both, with resultant changes in codon 137 from arginine to cysteine or leucine. These novel mutations cause constitutive activation of the receptor and are the likely cause of the patients' SIADH-like clinical picture, which we have termed "nephrogenic syndrome of inappropriate antidiuresis."

Commentaires: A partir de l'analyse de deux cas de syndrome inapproprié de sécrétion d'ADH (SIADH) avec un taux d'AVP bas, les auteurs ont émis l'hypothèse qu'il pouvait y avoir une activation constitutive du récepteur de la vasopressine. L'étude du gène AVPR2 a permi de mettre en évidence une mutation impliquant l'arginine en position 137 chez chacun des patients(R137C et R137L). Curieusement, cette même arginine est remplacée dans certains diabète insipide néphrogénique (R137H), il s'agit alors bien sur d'une mutation inactivatrice.

Les auteurs suggèrent que cette pathologie n'est pas si rare et recommandent d'étudier le gène AVPR2 si l'AVP est basse chez un enfant ayant un SIADH.

RS

Un partenaire inattendu dans le réseau des protéines du diaphragme de fente.

TRPC6 is a glomerular slit diaphragm-associated channel required for normal renal function

Reiser J, Polu KR, Moller CC, Kenlan P, Altintas MM, Wei C, Faul C, Herbert S, Villegas I, Avila-Casado C, McGee M, Sugimoto H, Brown D, Kalluri R, Mundel P, Smith PL, Clapham DE, Pollak MR.

Nat Genet. 2005 May 27

Progressive kidney failure is a genetically and clinically heterogeneous group of disorders. Podocyte foot processes and the interposed glomerular slit diaphragm are essential components of the permeability barrier in the kidney. Mutations in genes encoding structural proteins of the podocyte lead to the development of proteinuria, resulting in progressive kidney failure and focal segmental glomerulosclerosis. Here, we show that the canonical transient receptor potential 6 (TRPC6) ion channel is expressed in podocytes and is a component of the glomerular slit diaphragm. We identified five families with autosomal dominant focal segmental glomerulosclerosis in which disease segregated with mutations in the gene TRPC6 on chromosome 11q. Two of the TRPC6 mutants had increased current amplitudes. These data show that TRPC6 channel activity at the slit diaphragm is essential for proper regulation of podocyte structure and function.Commentaire: Le groupe de Martin Pollack (Boston) publie dans Nature Genetics du mois de Mai un article montrant la présence de mutation dans le gène TRPC6 codant pour un canal dont le rôle semble essentiel pour le bon fonctionnement de la barrière de filtration glomérulaire. Ce canal est localisé au même endroit dans le podocyte que la néphrine et la podocine avec lesquelles il interagit directement. Des mutations sont retrouvées dans 5 familles avec une HSF tardive se transmettant sur le mode autosomique dominant. Deux de ces mutations entrainnent%

Analyse du poids de naissance chez les jumeaux

Birth Weight and Creatinine Clearance in Young Adult Twins: Influence of Genetic, Prenatal, and Maternal Factors.
J Am Soc Nephrol. 2005 Jun 8

Previous studies have shown that low birth weight (LBW) is a risk factor for renal impairment in adult life. The effects of LBW and renal function were studied by using twins, which allows distinguishing among fetoplacental, maternal, and genetic influences. Perinatal data were obtained at birth, and absolute creatinine clearance (not corrected for body surface area) was measured at a mean age of 25.6 yr in 653 individuals. Twins were considered both as individuals and as members of twin pairs. Statistical analyses were performed with and without adjusting for gestational age, zygosity, gender, age, body mass index, glucose level, BP, and smoking status. Creatinine clearance was 4 ml/min lower in twins with LBW (<2500 g) than in twins with a high birth weight (P < 0.04, adjusted). Intrapair birth weight difference correlated positively with the intrapair difference in creatinine clearance equally in monozygotic and dizygotic twins (r = 0.35, P < 0.0001; r = 0.43, P < 0.0001, respectively). This suggests that fetoplacental factors are related to renal function and that genetic factors are less important. There was no significant difference in creatinine clearance between twins who both had LBW as compared with twins who both had a high birth weight. This may suggest that maternal factors, which influence the relation between LBW and renal function, are less important. LBW is related to a lower creatinine clearance at adult age. This relationship is probably due to fetoplacental factors. Surprising, genetic and maternal factors seem less important.

Commentaire: la première étude à ma connaissance de ce type qui indique assez clairement même si les différences de clairance ne sont pas énormes que le poids de naissance influe la filtration glomérulaire à long terme. L'effet "maternel" et les facteurs génétiques n'interviennent à priori pas ici.

Création du Blog Nephroped

Chers amis,

Nous avions émis l'idée de partager au sein de notre groupe nos lectures en créant une sorte de "journal club" par l'intermédiaire d' internet. Le blog pourrait bien être une solution simple et efficace pour réaliser ce projet. Je vous propose d'essayer. Je n'ai personnellement aucune expérience en la matière, nous faisons nos premiers pas ensemble !

Ce blog ne remplace en aucune façon le site web de la SNP mené de mains de maitre par Vincent Guigonis, par contre il pourrait peut-être compléter avantageusement notre liste de diffusion par e-mail (à voir).

Dans un premier temps je vous propose de nous limiter à signaler des articles qui nous ont semblé intéressants en transmettant sur le blog l'abstract tel qu'il apparait dans PubMed et en y ajoutant un commentaire personnel de quelques lignes. Bien entendu l'article est alors ouvert à discussion et chacun peut y aller de son commentaire.

Rémi Salomon