Intraperitoneal Pressure in Children: Fill-Volume Related and Impacted by Body Mass Index

♦ Objective

Prescription of intraperitoneal volume (IPV) in children on peritoneal dialysis (PD) should be individualized in order to optimize both efficiency and tolerance. Intraperitoneal pressure (IPP) can be used as an objective assessment of IPV. Despite IPP being correlated with IPV, there is an important interindividual variability presumed to be secondary to other implicated factors.

♦ Design

Over the past 2 years, we conducted a prospective study in our patients on PD ( N = 17). For each child, we recorded, at every third month of follow-up, IPV (in milliliters per square meter body surface area), age, gender, body mass index (BMI), and IPP (measured as centimeters of water), collecting a total of 53 data points.

♦ Results

There was a positive correlation between IPV and IPP ( r= 0.36), but this correlation was weak in contrast to the strong correlation noted between BMI and IPP ( r= 0.82). Age had a different influence on IPP: in the younger-aged group (< 2 years), IPP decreased with age; in the older-aged group (≥ 2 years), IPP increased with age. In some infants, we noted a paradoxical result: a low IPV with a high IPP.

♦ Conclusions

The strong correlation noted between IPP and BMI gives a better understanding of the interindividual variability of the previously described unique relationship between IPP and IPV. The more obese the child ( i.e., the higher the BMI), the higher is his IPP for a fixed IPV.

Mutations in KEOPS-complex genes cause nephrotic syndrome with primary microcephaly

Galloway-Mowat syndrome (GAMOS) is an autosomal-recessive disease characterized by the combination of early-onset nephrotic syndrome (SRNS) and microcephaly with brain anomalies. Here we identified recessive mutations in OSGEP, TP53RK, TPRKB, and LAGE3, genes encoding the four subunits of the KEOPS complex, in 37 individuals from 32 families with GAMOS. CRISPR-Cas9 knockout in zebrafish and mice recapitulated the human phenotype of primary microcephaly and resulted in early lethality. Knockdown of OSGEP, TP53RK, or TPRKB inhibited cell proliferation, which human mutations did not rescue. Furthermore, knockdown of these genes impaired protein translation, caused endoplasmic reticulum stress, activated DNA-damage-response signaling, and ultimately induced apoptosis. Knockdown of OSGEP or TP53RK induced defects in the actin cytoskeleton and decreased the migration rate of human podocytes, an established intermediate phenotype of SRNS. We thus identified four new monogenic causes of GAMOS, describe a link between KEOPS function and human disease, and delineate potential pathogenic mechanisms.

Worldwide view of nephropathic cystinosis: results from a survey from 30 countries

BACKGROUND

Nephropathic cystinosis is a rare inherited metabolic disorder leading to progressive renal failure and extra-renal comorbidity. The prognosis relies on early adherence to cysteamine treatment and symptomatic therapies. Developing nations [DiN] experience many challenges for management of cystinosis. The aim of this study was to assess the management characteristics in DiN compared with developed nations [DeN].

METHODS

A questionnaire was sent between April 2010 and May 2011 to 87 members of the International Pediatric Nephrology Association, in 50 countries.

RESULTS

A total of 213 patients were included from 41 centres in 30 nations (109 from 17 DiN and 104 from 13 DeN). 7% of DiN patients died at a median age of 5 years whereas no death was observed in DeN. DiN patients were older at the time of diagnosis. In DiN, leukocyte cystine measurement was only available in selected cases for diagnosis but never for continuous monitoring. More patients had reached end-stage renal disease in DiN (53.2 vs. 37.9%, p = 0.03), within a shorter time of evolution (8 vs. 10 yrs., p = 0.0008). The earlier the cysteamine treatment, the better the renal outcome, since the median renal survival increased up to 16.1 [12.5-/] yrs. in patients from DeN treated before the age of 2.5 years of age (p = 0.0001). However, the renal survival was not statistically different between DeN and DiN when patients initiated cysteamine after 2.5 years of age. The number of transplantations and the time from onset of ESRD to transplantation were not different in DeN and DiN. More patients were kept under maintenance dialysis in DiN (26% vs.19%, p = 0.02); 79% of patients from DiN vs. 45% in DeN underwent peritoneal dialysis.

CONCLUSIONS

Major discrepancies between DiN and DeN in the management of nephropathic cystinosis remain a current concern for many patients living in countries with limited financial resources.

Clinical and molecular findings in three Moroccan families with distal renal tubular acidosis and deafness: Report of a novel mutation of ATP6V1B1 gene

BACKGROUND

Primary distal renal tubular acidosis (dRTA) is a rare genetic condition characterized by an impaired acid excretion by the intercalated cells in the renal collecting duct. Recessive forms of this disease are caused by mutations in tow major genes: ATP6V1B1 and ATP6V0A4. Causal mutations in ATP6V1B1 gene are classically associated with early sensorineural hearing loss, however cases of tubular acidosis with early deafness have also been described in patients with mutations in the ATP6V0A4 gene.

METHODS

The phenotype and genotype of three Moroccan consanguineous families with dRTA and deafness were assessed. Molecular analysis was performed by PCR amplification and direct sequencing of exon 12 of ATP6V1B1 gene.

RESULTS

A novel c.1169dupC frameshift mutation of ATP6V1B1 gene was identified in one family and the c.1155dupC North African mutation in the tow other families.

DISCUSSION AND CONCLUSION

In this report, we propose first line genetic testing based on screening of these two mutations both located in exon 12 of ATP6V1B1 gene in Moroccan patients with recessive form of dRTA associated to precocious hearing loss. Molecular diagnosis of dRTA leads to appropriate treatment and prevention of renal failure in affected individuals and to provide genetic counseling for families at risk.

AGXT Gene Mutations and Prevalence of Primary Hyperoxaluria Type 1 in Moroccan Population

INTRODUCTION

Primary hyperoxaluria type 1 (PH1) is an autosomal recessive disorder caused by deficiency of alanine glyoxylate aminotransferase, due to a defect in the AGXT gene. Several mutations in this gene have been reported and some of them have been observed in multiple populations. The aim of our study was to analyze the mutations causing PH1 in the Moroccan population and to estimate its prevalence in Morocco.

METHODS

Molecular studies of 29 unrelated Moroccan patients with PH were performed by direct sequencing of all exons of the AGXT gene. In addition, to estimate the prevalence of PH1, we screened for the recurrent p.Ile244Thr mutation in 250 unrelated Moroccan newborns using real-time polymerase chain reaction.

RESULTS

Four pathogenic mutations were detected in 25 unrelated patients. The c.731T>C (p.Ile244Thr) was the most frequent mutation with a frequency of 84%. The other three mutations were c.33delC, c.976delG, and c.331C>T. The prevalence of the PH1 mutation among Moroccans was then estimated to range from 1/7267 to 1/6264.

CONCLUSION

PH1 is one of the most prevalent genetic diseases in the Moroccan population and is probably underdiagnosed. Front line genetic testing for PH1 in Morocco should be initiated using an assay for the recurrent p.Ile244Thr mutation. This strategy would provide a useful tool for precocious diagnosis of presymptomatic individuals and to prevent their rapid progression to renal failure.

Mutation Update of the CLCN5 Gene Responsible for Dent Disease 1

Dent disease is a rare X-linked tubulopathy characterized by low molecular weight proteinuria, hypercalciuria, nephrocalcinosis and/or nephrolithiasis, progressive renal failure, and variable manifestations of other proximal tubule dysfunctions. It often progresses over a few decades to chronic renal insufficiency, and therefore molecular characterization is important to allow appropriate genetic counseling. Two genetic subtypes have been described to date: Dent disease 1 is caused by mutations of the CLCN5 gene, coding for the chloride/proton exchanger ClC-5; and Dent disease 2 by mutations of the OCRL gene, coding for the inositol polyphosphate 5-phosphatase OCRL-1. Herein, we review previously reported mutations (n = 192) and their associated phenotype in 377 male patients with Dent disease 1 and describe phenotype and novel (n = 42) and recurrent mutations (n = 24) in a large cohort of 117 Dent disease 1 patients belonging to 90 families. The novel missense and in-frame mutations described were mapped onto a three-dimensional homology model of the ClC-5 protein. This analysis suggests that these mutations affect the dimerization process, helix stability, or transport. The phenotype of our cohort patients supports and extends the phenotype that has been reported in smaller studies.

Intraperitoneal pressure in children: fill-volume related and impacted by body mass index

OBJECTIVE

Prescription of intraperitoneal volume (IPV) in children on peritoneal dialysis (PD) should be individualized in order to optimize both efficiency and tolerance. Intraperitoneal pressure (IPP) can be used as an objective assessment of IPV. Despite IPP being correlated with IPV, there is an important interindividual variability presumed to be secondary to other implicated factors.

DESIGN

Over the past 2 years, we conducted a prospective study in our patients on PD (N = 17). For each child, we recorded, at every third month of follow-up, IPV (in milliliters per square meter body surface area), age, gender, body mass index (BMI), and IPP (measured as centimeters of water), collecting a total of 53 data points.

RESULTS

There was a positive correlation between IPV and IPP (r = 0.36), but this correlation was weak in contrast to the strong correlation noted between BMI and IPP (r = 0.82). Age had a different influence on IPP: in the younger-aged group (< 2 years), IPP decreased with age; in the older-aged group (> 2 years), IPP increased with age. In some infants, we noted a paradoxical result: a low IPV with a high IPP.

CONCLUSIONS

The strong correlation noted between IPP and BMI gives a better understanding of the interindividual variability of the previously described unique relationship between IPP and IPV. The more obese the child (i.e., the higher the BMI), the higher is his IPP for a fixed IPV.

Effects of automated peritoneal dialysis on residual daily urinary volume in children

Preservation of residual renal function (RRF) is an important goal. In children, a more rapid decline in RRF has been observed under hemodialysis (HD) therapy as compared with peritoneal dialysis (PD) therapy. In adults, however, automated peritoneal dialysis (APD) may cause a more rapid decline of RRF than continuous ambulatory peritoneal dialysis (CAPD) does. The objective of the present study, a survey in a single center over the last 15 years, was to assess the impact of APD versus hemodiafiltration (HDF) on daily urinary volume (dUV) outcome. We included 97 children who were dialyzed for at least a 12-month period between January 1985 and December 1999, using either HDF (n = 60; 62%) or PD [n = 37; 38% (86% of those on APD)]. The endpoint was anuria occurrence, defined as a dUV below 50 mL/m2 body surface area (BSA) at three consecutive monthly determinations. Despite the use of HDF as hemodialysis therapy (that is, biocompatible membranes and a very low incidence of vascular instability during ultrafiltration), PD--even predominantly prescribed as APD--was associated with better preservation of residual dUV. At dialysis end, anuria occurred in 65% of the children undergoing HD as compared with 23% of those undergoing PD. The mean age of the children at dialysis start was lower in the PD group. No other significant differences were noted between the groups, either for the rate of uropathies or for the RRF at initiation of dialysis.