Dorota Drozdz

Genetic screening in adolescents with steroid-resistant nephrotic syndrome

Genetic screening paradigms for congenital and infantile nephrotic syndrome are well established; however, screening in adolescents has received only minor attention. To help rectify this, we analyzed an unselected adolescent cohort of the international PodoNet registry to develop a rational screening approach based on 227 patients with nonsyndromic steroid-resistant nephrotic syndrome aged 10-20 years. Of these, 21% had a positive family history. Autosomal dominant cases were screened for WT1, TRPC6, ACTN4, and INF2 mutations. All other patients had the NPHS2 gene screened, and WT1 was tested in sporadic cases. In addition, 40 sporadic cases had the entire coding region of INF2 tested. Of the autosomal recessive and the sporadic cases, 13 and 6%, respectively, were found to have podocin-associated nephrotic syndrome, and 56% of them were compound heterozygous for the nonneutral p.R229Q polymorphism. Four percent of the sporadic and 10% of the autosomal dominant cases had a mutation in WT1. Pathogenic INF2 mutations were found in 20% of the dominant but none of the sporadic cases. In a large cohort of adolescents including both familial and sporadic disease, NPHS2 mutations explained about 7% and WT1 4% of cases, whereas INF2 proved relevant only in autosomal dominant familial disease. Thus, screening of the entire coding sequence of NPHS2 and exons 8-9 of WT1 appears to be the most rational and cost-effective screening approach in sporadic juvenile steroid-resistant nephrotic syndrome.

Assessment of long-term renal complications in extremely low birth weight children

We assessed the long-term renal complications in a regional cohort of extremely low birth weight (ELBW) children born in 2002–2004. The study group, comprising 78 children born as ELBW infants (88% of the available cohort), was evaluated with measurement of serum cystatin C, urinary albumin excretion, renal ultrasound, and 24-h ambulatory blood pressure measurements. The control group included 38 children born full-term selected from one general practice in the district. Study patients were evaluated at a mean age of 6.7xa0years, and had a median birthweight of 890xa0g (25th–75th percentile: 760–950xa0g) and a median gestational age of 27xa0weeks (25th–75th percentile: 26–29xa0weeks). Mean serum cystatin C levels were significantly higher (0.64 vs. 0.59xa0mg/l; pu2009=u20090.01) in the ELBW group. Hypertension was diagnosed in 8/78 ELBW and 2/38 of the control children (pu2009=u20090.5). Microalbuminuria (>20xa0mg/g of creatinine) was detected only in five ELBW children (pu2009=u20090.17). The mean renal volume was significantly lower in the ELBW group (absolute kidney volume 81xa0ml vs. 113xa0ml; pu2009<u20090.001, relative kidney volume 85 vs. 97%; pu2009<u20090.001). Abnormally small kidneys (<2/3 of predicted size) were detected in 19 ELBW and four control children (pu2009=u20090.08). Multivariate logistic regression revealed that the only independent risk factor for renal complications was weight gained during neonatal hospitalization (odds ratio: 0.67; 95% confidence interval: 0.39–0.94). Serum cystatin C and kidney volume are significantly lower in school-age ELBW children. It is important to include systematic renal evaluation in the follow-up programs of ELBW infants.

Skin autofluorescence as a marker of cardiovascular risk in children with chronic kidney disease

BackgroundWe examined skin autofluorescence (sAF) in chronic kidney disease children (CKD) in relation to renal function and dialysis modality.MethodsTwenty children on hemodialysis (HD), 20 on peritoneal dialysis (PD), 36 treated conservatively, and 26 healthy subjects were enrolled into the study. In all children sAF, pulse-wave velocity indexed to height (PWV/ht), left ventricular mass index (LVMI), blood pressure (BP), serum lipid profile, phosphate (P), calcium (Ca), and homocysteine were measured.ResultssAF was significantly elevated in CKD groups vs. controls and was significantly associated with PWV/ht, LVMI, BP, P, Caxa0×xa0P product and homocysteine. sAF in HD and PD groups was positively correlated with dialysis vintage, and in the predialysis group negatively correlated with glomerular filtration rate (eGFR). Multiple regression analysis showed significant association of sAF with LVMI and P in the CKD patient group, and with dialysis treatment duration and BP in dialyzed children.ConclusionsIn CKD children, tissue accumulation of advanced glycation end-products (AGEs) was observed. This was aggravated as eGFR declined and was related to early cardiovascular changes and some biochemical cardiovascular disease (CVD) risk markers. sAF as a non-invasive method may be a useful tool for identification of a clinical risk factors of cardiovascular disease in CKD children.

Mutational analysis in podocin-associated hereditary nephrotic syndrome in Polish patients: founder effect in the Kashubian population

Hereditary nephrotic syndrome is caused by mutations in a number of different genes, the most common being NPHS2. The aim of the study was to identify the spectrum of NPHS2 mutations in Polish patients with the disease. A total of 141 children with steroid-resistant nephrotic syndrome (SRNS) were enrolled in the study. Mutational analysis included the entire coding sequence and intron boundaries of the NPHS2 gene. Restriction fragment length polymorphism (RFLP) and TaqMan genotyping assay were applied to detect selected NPHS2 sequence variants in 575 population-matched controls. Twenty patients (14xa0%) had homozygous or compound heterozygous NPHS2 mutations, the most frequent being c.1032delT found in 11 children and p.R138Q found in four patients. Carriers of the c.1032delT allele were exclusively found in the Pomeranian (Kashubian) region, suggesting a founder effect origin. The 14xa0% NPHS2 gene mutation detection rate is similar to that observed in other populations. The heterogeneity of mutations detected in the studied group confirms the requirement of genetic testing the entire NPHS2 coding sequence in Polish patients, with the exception of Kashubs, who should be initially screened for the c.1032delT deletion.

Skin autofluorescence as a novel marker of vascular damage in children and adolescents with chronic kidney disease.

BackgroundSkin autofluorescence (sAF) was examined as a marker of the accumulation of advanced glycation end products (AGEs) in tissues of children with chronic kidney disease (CKD) in relation to renal function, dialysis modality and markers of endothelial inflammation and dysfunction.MethodsA total of 76 children with CKD were enrolled in the study, of whom 20 children were on hemodialysis (HD), 20 were on peritoneal dialysis (PD) and 36 were treated conservatively. A control group of 26 healthy subjects was also included in the study. In all children, sAF intensity, carotid intima-media (cIMT) thickness and plasma concentrations of sE-selectin, matrix metalloproteinase 9 (MMP-9), tissue inhibitor of metalloproteinase 1 (TIMP-1), asymmetric dimethylarginine (ADMA), symmetric dimethylarginine (SDMA) and plasminogen activator inhibitor type 1 (PAI-1) were measured.ResultsCompared to the controls, children with CKD had significantly elevated sAF levels. sAF in the children with CKD was positively correlated with sE-selectin, MMP-9, TIMP-1, ADMA, SDMA and PAI-1 levels. In the predialysis group (conservative treatment) sAF levels were positively correlated with sE-selectin and ADMA levels and negatively correlated with glomerular filtration rate. Multiple regression analysis showed a significant association of sAF with sE-selectin and MMP-9 in CKD children.ConclusionsThe results reveal that AGEs were accumulated in the children with CKD. This accumulation was related to early vascular changes and a number of biochemical vascular risk markers. sAF measurement, as a noninvasive method, may be useful for identification of clinical risk factors of vascular disease in CKD children.

Which equations should and which should not be employed in calculating eGFR in children

PURPOSEnWe assessed the reliability of calculating eGFR in children as compared to the iohexol disappearance test (GFR-I), which was performed 417 times in 353 children aged 2 and more.nnnMATERIAL/METHODSneGFR was estimated with equations based on serum creatinine: Schwartz (1: eGFR-Scr), Cockroft-Gault (2: eGFR-CG) and MDRD (3: eGFR-MDRD), and on creatinine clearance (4: eGFR-U), or relying on serum cystatin C: Hoeck (5: eGFR-H), Bokenkamp (6: eGFR-B) and Filler (7: eGFR-F), and on the three Schwartz markers (8: eGFR-S3M). Mean relative error (RE), correlation (R), Bland-Altman analysis and accuracy of GFR-I were studied in all patients and in subgroups: at GFR<60ml/min/1.73m(2); in children aged ≤12 and >12.nnnRESULTSnThe results by eGFR-Scr, eGFR-S3M demonstrated no statistical difference to GFR-I at GFR<60ml/min/1.73m(2), but underestimated eGFR at higher filtration values by 11.6±15.1% and 19.1±16.4, respectively (p<0.0000). The eGFR-B, eGFR-F and eGFR-MDRD equations illustrated important overestimation of reference GFR results (RE: 84±44.2%; 29.5±27.9%, 35.6±62%; p<0.0000 for all). The MDRD and C-G formulas showed statistically better consistency in children aged >12. A good agreement was achieved by the eGFR-H equation (5.1±21.9%; p<0.0000; R=0.78).nnnCONCLUSIONSn(1) Schwartz equations show a good conformity at GFR<60ml/min/1.73m(2), but underestimate the results at higher GFR values. (2) The Bokenkamp equation with original coefficient should not be employed in children. (3) The use of the Hoeck formula in all children and C-G and MDRD formula in children aged >12 is possible. (4) The error of eGFR calculations increases at higher GFR values.

Cardiovascular changes during chronic hypertensive states

It is well established that elevated blood pressure constitutes a major risk factor for coronary heart disease, arrythmias, heart failure, cerebrovascular disease, peripheral artery disease and renal failure. Blood pressure level and the duration of arterial hypertension (HTN) impact target organ damage. Many studies in adults have demonstrated the role of antihypertensive therapy in preventing cardiovascular (CV) events. The so-called hard end-points, such as death, myocardial infarction (MI) or stroke, are rarely seen in children, but intermediate target organ damage, including left ventricular hypertrophy, increased intima-media thickness and microalbuminuria, is already detectable during childhood. The goal of antihypertensive treatment is to reduce the global risk of CV events. In the adult population stratification of CV risk is based on blood pressure level, risk factors, subclinical target organ damage and established CV and kidney disease. Increased CV risk begins early in the course of kidney disease, and CV diseases are the most frequent cause of morbidity and mortality in patients with chronic kidney disease (CKD). Children with CKD are especially prone to the long-term effects of CV risk factors, which result in high morbidity and mortality in young adults. To improve the outcome, pediatric and adult CKD patients require nephro- and cardioprotection.

Effect of hypertension and antihypertensive medications on residual renal function in children treated with chronic peritoneal dialysis

PURPOSEnTo evaluate the effect of hypertension (HTN) and antihypertensive medications (AHM) on residual renal function (RRF) in children on CAPD and APD.nnnMATERIAL/METHODSnWe retrospectively evaluated underlying kidney disease, systolic and diastolic blood pressure (SBP/DBP), presence and control of HTN (SBP/DBP≥95th percentile), AHM, RRF (daily diuresis, residual glomerular filtration rate [rGFR]), biochemical parameters, BMI Z-score, and dialysis parameters during 12-month follow-up in 87 children (38 CAPD, 49 APD) aged 10.22±4.31 years. The rate of RRF loss was expressed as absolute and relative [%] reduction.nnnRESULTSnAt baseline, HTN was found in 74.7% patients (CAPD/APD: 84.2%/67.3%, P=0.06), most commonly in HUS and least frequently in CAKUT. The proportion of CAPD/APD patients with poorly controlled HTN was 70.0%/63.3% (P=0.50). Relative daily diuresis loss in children with uncontrolled HTN was higher (P=0.017) compared to children with SBP/DBP <95th percentile. No effect of AHM on the rate of RRF loss was found. In multivariate analysis, absolute daily diuresis loss was related to baseline diuresis (β=-0.30, P<0.001) and proteinuria (β=-0.31, P=0.004); absolute rGFR loss to baseline rGFR (β=-0.73, P<0.001) and glucose load after 12 months (β=-0.36, P=0.02); relative daily diuresis loss to mean BMI Z-score (β=-0.44, P=0.04); and relative rGFR to baseline rGFR (β=-0.37, P<0.001) and SBP percentile (β=-0.21, P=0.045).

Efficacy and safety of sevelamer carbonate in hyperphosphatemic pediatric patients with chronic kidney disease

BackgroundTreatment for hyperphosphatemia in chronic kidney disease (CKD) involves dietary control of phosphorus intake, dialysis, and treatment with oral phosphate binders, none of which were approved by the Federal Food and Drug Administration in pediatric patients at the time of this study.MethodsThis was a phase 2, multicenter study (NCT01574326) with a 2-week, randomized, placebo-controlled, fixed-dose period (FDP) followed by a 6-month, single-arm, open-label, dose-titration period (DTP), with the aim to evaluate the safety and efficacy of sevelamer carbonate (SC) in hyperphosphatemic pediatric patients with CKD. Following a 2–4xa0week screening phase, pediatric patients with a serum phosphorus level higher than age-appropriate levels were randomized to receive either SC or placebo as powder/tablets in 0.4–1.6xa0g doses, based on body surface area. The primary efficacy outcome was the change in serum phosphorus from baseline to end of the FDP in the SC versus placebo arms (analysis of covariance). The secondary outcome was mean change in serum phosphorus from baseline to end of DTP by treatment group and overall. Treatment-emergent/serious adverse events (AEs) were recorded.ResultsOf 101 enrolled patients (29 centers), 66 completed the study. The majority of patients were adolescents (74%; mean age 14.1xa0years) and on dialysis (77%). Renal transplant was the main reason for discontinuation. SC significantly reduced serum phosphorus from baseline levels (7.16xa0mg/dL) during the FDP compared to placebo (least square mean differencexa0−xa00.90xa0mg/dL, pxa0=xa00.001) and during the DTP (−xa01.18xa0mg/dL, pxa0<xa00.0001). The safety and tolerability of SC and placebo were similar during the FDP, with patients in both groups reporting mild/moderate gastrointestinal AEs during the DTP.ConclusionsSevelamer carbonate significantly lowered serum phosphorus levels in hyperphosphatemic children with CKD, with no serious safety concerns identified.

Neutral pH and low–glucose degradation product dialysis fluids induce major early alterations of the peritoneal membrane in children on peritoneal dialysis

The effect of peritoneal dialysates with low-glucose degradation products on peritoneal membrane morphology is largely unknown, with functional relevancy predominantly derived from experimental studies. To investigate this, we performed automated quantitative histomorphometry and molecular analyses on 256 standardized peritoneal and 172 omental specimens from 56 children with normal renal function, 90 children with end-stage kidney disease at time of catheter insertion, and 82 children undergoing peritoneal dialysis using dialysates with low-glucose degradation products. Follow-up biopsies were obtained from 24 children after a median peritoneal dialysis of 13 months. Prior to dialysis, mild parietal peritoneal inflammation, epithelial-mesenchymal transition and vasculopathy were present. After up to six and 12 months of peritoneal dialysis, blood microvessel density was 110 and 93% higher, endothelial surface area per peritoneal volume 137 and 95% greater, and submesothelial thickness 23 and 58% greater, respectively. Subsequent peritoneal changes were less pronounced. Mesothelial cell coverage was lower and vasculopathy advanced, whereas lymphatic vessel density was unchanged. Morphological changes were accompanied by early fibroblast activation, leukocyte and macrophage infiltration, diffuse podoplanin presence, epithelial mesenchymal transdifferentiation, and by increased proangiogenic and profibrotic cytokine abundance. These transformative changes were confirmed by intraindividual comparisons. Peritoneal microvascular density correlated with peritoneal small-molecular transport function by uni- and multivariate analysis. Thus, in children on peritoneal dialysis neutral pH dialysates containing low-glucose degradation products induce early peritoneal inflammation, fibroblast activation, epithelial-mesenchymal transition and marked angiogenesis, which determines the PD membrane transport function.