Familial forms of nephrotic syndrome.

The recent discovery of genes involved in familial forms of nephrotic syndrome represents a break-through in nephrology. To date, 15 genes have been characterized and several new loci have been identified, with a potential for discovery of new genes. Overall, these genes account for a large fraction of familial forms of nephrotic syndrome, but they can also be recognized in 10-20% of sporadic cases. These advances increase diagnostic and therapeutic potentials, but also add higher complexity to the scenario, requiring clear definitions of clinical, histopathological and molecular signatures. In general, genetic forms of nephrotic syndrome are resistant to common therapeutic approaches (that include steroids and calcineurin inhibitors) but, in a few cases, drug response or spontaneous remission suggest a complex pathogenesis. Finally, syndromic variants can be recognized on the basis of the associated extra-renal manifestations. In this educational review, clinical, histological and molecular aspects of various forms of familial nephrotic syndrome have been reviewed in an attempt to define a rational diagnostic approach. The proposed model focuses on practical and economic issues, taking into consideration the impossibility of using genetic testing as starting diagnostic tool. The final objective of this review is to outline a diagnostic flow-chart for clinicians and geneticists and to generate a rational scheme for molecular testing.

Longitudinal evaluation of mycophenolic acid pharmacokinetics in pediatric kidney transplant recipients. The role of post-transplant clinical and therapeutic variables.

This longitudinal study assessed the influence of post-transplant clinical and therapeutic variables in 50 kidney transplant recipients aged 2-19 yr receiving a triple immunosuppressive regimen consisting of cyclosporine microemulsion (CsA), steroids and MMF (300-400 mg/m(2) body surface area twice daily), the full pharmacokinetic profile (10 points) of which was investigated on post-transplant days 6, 30, 180 and 360. Total plasma MPA was measured by Enzyme Multiplied Immunoassay Technique. CsA therapeutic drug monitoring (TDM) was performed via C2 blood monitoring, while MPA TDM via C0. MPA Cmax, tmax, AUC0-12 and AUC0-4 pharmacokinetic profile changed significantly during the first post-transplant year. C0 was a poor predictor of the total MPA exposure [as measured by the area under the concentration-time curve AUC)], while a truncated AUC was a good surrogate of the 12-h profile (r = 0.91; p < 0.001) Graft function and cyclosporine therapy influenced MPA pharmacokinetics, as shown by the univariate and multivariate analyses. We conclude that because after transplantation MPA exposure varied over time, a strict TDM is advisable in the pediatric population.

Recurrent lymphomatoid papulosis associated with nephrotic syndrome. An occurrence of uncertain origin.

We report on a 10-year-old child with nephrotic syndrome who developed recurrent lymphomatoid papulosis (LYP) 60 months after the first episode of proteinuria. LYP appeared when the child was taking low-dose cyclosporin and disappeared after the drug was replaced by prednisone at doses utilized for nephrotic syndrome (2 mg/kg). During the tapering of steroids, when the child was treated with low-dose prednisone (0.2 mg/kg), both LYP and nephrotic syndrome started again and required the reintroduction of prednisone to restore a normal clinical situation. This is the first case of LYP occurring in concomitance and synchronous with nephrotic syndrome. LYP was unrelated to cyclosporin (second episode after its withdrawn) but preceded the recurrence of proteinuria, suggesting a relationship with the disease activity. Even though the etiology of LYP is, in this case, uncertain, it should be considered as a clinical association of nephrotic syndrome in children and also included among potential triggers of the disease.

Selection of modalities, prescription, and technical issues in children on peritoneal dialysis.

Peritoneal dialysis (PD) is widely employed as a dialytic therapy for uraemic children, especially in its automated form (APD), that is associated with less burden of care on patient and family than continuous ambulatory PD. Since APD offers a wide range of treatment options, based on intermittent and continuous regimens, prescription can be individualized according to patient's age, body size, residual renal function, nutritional intake, and growth-related metabolic needs. Transport capacity of the peritoneal membrane of each individual patient should be assessed, and regularly monitored, by means of standardized peritoneal function tests validated in pediatric patients. To ensure maximum recruitment of peritoneal exchange area, fill volume should be scaled to body surface area and adapted to each patient, according to clinical tolerance and intraperitoneal pressure. PD solutions should be employed according to their biocompatibility and potential ultrafiltration capacity; new pH-neutral, glucose-free solutions can be used in an integrated way in separate dwells, or by appropriately mixing during the same dialytic session. Kinetic modelling software programs may help in the tailoring of PD prescription to individual patients' characteristics and needs. Owing to advances in the technology of new APD machines, greater programming flexibility, memorized delivery control, and tele-dialysis are currently possible.

Cyclosporin and organ specific toxicity: clinical aspects, pharmacogenetics and perspectives.

Cyclosporine (CsA) has considerably modified the graft survival in solid organ and bone marrow transplantations. It is also the treatment of choice in chronic diseases such as steroid resistance and/or dependence nephrotic syndrome and autoimmune-diseases, especially in those cases that require long term treatments. Renal toxicity is the major adverse effect of chronic CsA administration. Deterioration of renal function and renal histopathology are the basic elements of the diagnosis. Overall, available studies suggest a good degree of safety related to appropriate drug dosages even if they require an adequate degree of surveillance in case of rapid changes of renal functions and long term evaluation of renal pathology. CsA neurotoxicity is the second major problem that seems underestimated especially in case of subtle manifestations in children. The full blown picture of the acute form is characterized by convulsion and sudden alteration of mental function that are reversible upon drug withdrawal. The diagnosis is based on typical CT and MRI aspects of extensive bilateral white-matter abnormalities in the occipital region of the brain that mimics the posterior encephalopathy syndrome. Prospective evaluations of drug tolerance include renal histology in case of chronic renal toxicity and neuro-imaging to identify and block acute neurotoxicity.

Protracted remission of proteinuria after combined therapy with plasmapheresis and anti-CD20 antibodies/cyclophosphamide in a child with oligoclonal IgM and glomerulosclerosis.

We describe a child presenting with oligoclonal plasma IgM (1.2 g%) and nephrotic syndrome with focal segmental glomerulosclerosis. Oligoclonality was demonstrated by the analysis of the complementary determining region 3 (CDR 3) on immunoglobulin heavy chains and by two dimensional electrophoresis and Western blot analysis that showed the bulk of isoforms having a cationic muU chain compared with the normal homologue (pI 7.5 vs 6.5). Urinary light chains were absent, and bone marrow aspirate was normal. Usual therapies for nephrotic syndrome with steroids and cyclosporin were useless. At the age of 9 years the patient was treated with plasmapheresis plus cyclophosphamide (2 mg/kg per day for 60 days), which temporarily reduced plasma IgM, and proteinuria was normal for 3 years. After this period, due to new recurrence of nephrotic syndrome, the patient received a cycle with anti-CD20 antibodies (500 mg/m(2) every week for a month) associated with a cycle of plasmapheresis that normalized proteinuria again, and, after 3 years, the proteinuria is still in remission. This is the first case of nephrotic syndrome associated with oligoclonal plasma IgM and mesangial IgM deposits. Both cyclophosphamide and anti-CD20 antibodies associated with plasmapheresis induced, at different stages, stable and protracted remission of proteinuria without evident side effects. Long term efficacy and safety of the association are still to be determined.

Laparoscopic-assisted peritoneal dialysis catheter implantation in pediatric patients.

OBJECTIVES: To assess the feasibility and complications of laparoscopic-assisted placement of peritoneal dialysis catheters (PDCs) in pediatric patients. METHODS: A total of 15 patients undergoing laparoscopic-assisted PDC insertion were studied. A single 10-mm epigastric port was used, unless concomitant diseases were present. A double-cuffed straight Tenckhoff catheter was implanted, with the deep cuff placed within a preperitoneal tunnel underneath the left rectus muscle. The catheter tip was positioned in the left iliac fossa by stylet wire manipulation under laparoscopic control, with the exit site oriented laterally or downward. Subtotal omentectomy was performed by way of the epigastric port site. The findings were compared with those of a group of patients undergoing open PDC insertion. RESULTS: The median operating time was not different in the two groups. In the laparoscopic group, a single port was used in 9 cases, and adhesiolysis was performed in 2. The median time to PD initiation was not different in the two groups, nor were any significant differences found in the infectious complications, leak or obstruction rates, or need for secondary surgical revisions between the two groups. Surgical revision was necessary because of peritonitis in 1, persistent leak in 1, and dislodgement in 2 in the open group and because of blockages in 3 in the laparoscopic group. Laparoscopy allowed for the rescue of two such catheters. CONCLUSIONS: The results of our study have shown that laparoscopy allows for careful assessment of the abdominal cavity, recognition and treatment of intraabdominal diseases, and precise placement of PDCs. However, it does not seem to reduce the early catheter-related complication rate. Mechanical obstruction remains a common cause of early catheter malfunction. However, laparoscopy can allow for the rescue of blocked catheters.

Genetic approaches to human renal agenesis/hypoplasia and dysplasia.

Congenital abnormalities of the kidney and urinary tract are frequently observed in children and represent a significant cause of morbidity and mortality. These conditions are phenotypically variable, often affecting several segments of the urinary tract simultaneously, making clinical classification and diagnosis difficult. Renal agenesis/hypoplasia and dysplasia account for a significant portion of these anomalies, and a genetic contribution to its cause is being increasingly recognized. Nevertheless, overlap between diseases and challenges in clinical diagnosis complicate studies attempting to discover new genes underlying this anomaly. Most of the insights in kidney development derive from studies in mouse models or from rare, syndromic forms of human developmental disorders of the kidney and urinary tract. The genes implicated have been shown to regulate the reciprocal induction between the ureteric bud and the metanephric mesenchyme. Strategies to find genes causing renal agenesis/hypoplasia and dysplasia vary depending on the characteristics of the study population available. The approaches range from candidate gene association or resequencing studies to traditional linkage studies, using outbred pedigrees or genetic isolates, to search for structural variation in the genome. Each of these strategies has advantages and pitfalls and some have led to significant discoveries in human disease. However, renal agenesis/hypoplasia and dysplasia still represents a challenge, both for the clinicians who attempt a precise diagnosis and for the geneticist who tries to unravel the genetic basis, and a better classification requires molecular definition to be retrospectively improved. The goal appears to be feasible with the large multicentric collaborative groups that share the same objectives and resources.

Effect of carnitine supplementation on lipid profile and anemia in children on chronic dialysis.

We prospectively evaluated the effects of L-carnitine supplementation on plasma free carnitine (FC) levels, serum lipid profile, and erythropoietin (rhEPO) requirement in 24 children treated with peritoneal dialysis (PD; n=16) or hemodialysis (HD; n=8). The study was divided into a 3-month observation period, and a 3-month treatment period during which patients received 20 mg/kg per day of L-carnitine given orally. Clinical, biochemical, and hematological data were collected every 3 months. FC levels were measured in plasma and peritoneal dialysate by tandem mass spectrometry. There were no statistically significant changes in lipid levels, hemoglobin, or rhEPO requirements during the course of the study. Fifteen patients (13 PD, 2 HD) had plasma FC levels measured before and after treatment; FC levels increased from 32.1 +/- 14.1 micromol/l to 80.9 +/- 38.7 micromol/l (P<0.001). In PD patients, dialysate FC losses increased from 106 +/- 78 micromol/day at baseline to 178 +/- 119 micromol/day after supplementation. Positive correlations between FC plasma levels and dialysate levels (R=0.507) or daily excretion (R=0.603) were found after treatment. In our case series, an oral dose of 20 mg/kg per day of L-carnitine restored FC levels and produced a positive carnitine balance with no significant effects on hematological parameters or lipid profile over a 3-month period. Prolonged treatment duration may be required to obtain significant results.

Repetitive fragmentation products of albumin and alpha1-antitrypsin in glomerular diseases associated with nephrotic syndrome.

Even if nephrotic syndrome is characterized by massive urinary loss of major plasma proteins, a clear structural characterization based on proteomics has never been reported. Urine and plasma of 23 patients with different idiopathic nephrotic syndromes (10 steroid-sensitive minimal-change nephropathy, seven steroid-resistant FSGS, and six membranous glomerulonephritis) were analyzed with two-dimensional electrophoresis in soft gel, Western blot, and matrix-assisted laser desorption/ionization time of flight mass spectrometry; 72 urinary components corresponded to fragments of albumin and/or of alpha1-antitrypsin. Several repetitive fragmentation motives and a few differences among different pathologies were found. Several (21 of 72) urinary albumin fragments also were detected in plasma, although in lower concentration, suggesting a preferential excretion. The bulk of components with low molecular weight were detected only in urine, suggesting an in situ formation; zymograms with albumin as substrate showed the presence in urine of specific proteases. A final but not secondary point was the characterization of albumin adducts that harbor both the COOH and NH2 terminal parts of the protein, suggesting the formation of new covalent chemical groups. Altogether, these new findings reveal unexpected structural and functional aspects of proteinuria that may play a key role in pathogenesis. Characterization of urinary fragmentation patterns should be extended to other renal diseases.

WT1 mutations in nephrotic syndrome revisited. High prevalence in young girls, associations and renal phenotypes.

WT1 mutations have been considered a rare cause of nephrotic syndrome but recent reports challenge this assumption. Exclusion of inherited forms is a basic point in any therapeutic strategy to nephrotic syndrome since they do not respond to drugs. We screened for WT1 mutations in 200 patients with nephrotic syndrome: 114 with steroid resistance (SRNS) and 86 with steroid dependence (SDNS) for whom other inherited forms of nephrotic syndrome (NPHS2, CD2AP) had been previously excluded. Three girls out of 32 of the group with steroid resistance under 18 years presented classical WT1 splice mutations (IVS9+5G>A, IVS9+4C>T) of Frasier syndrome. Another one presented a mutation coding for an amino acid change (D396N) at exon 9 that is typical of Denys-Drash syndrome. All presented resistance to drugs and developed end stage renal failure within 15 years. Two girls of the Frasier group presented a 46 XY karyotype with streak gonads while one was XX and had normal gonad morphology. In the two cases with IVS9+5G>A renal pathology was characterized by capillary wall thickening with deposition of IgG and C3 in one that was interpreted as a membrane pathology. Foam cells were diffuse in tubule-interstitial areas. In conclusion, WT1 splice mutations are not rare in females under 18 years with SRNS. This occurs in absence of a clear renal pathology picture and frequently in absence of phenotype change typical of Frasier syndrome. In adults and children with SDNS, screening analysis is of no clinical value. WT1 hot spot mutation analysis should be routinely done in children with SRNS; if the molecular screening anticipates any further therapeutic approach it may modify the long term therapeutic strategy.

Transitions of serum albumin in patients with glomerulosclerosis 'in vivo' characterization by electrophoretic titration curves.

HSA functions as a physiological transporter of solutes and small molecules that induce structural transitions 'in vitro'. Analysis of these transitions requires prior purification of HSA that could introduce bias due to conformational changes. We utilized electrophoretic titration curves to describe a neutral to acid (N-A) transition of HSA directly in sera of seven patients with active focal segmental glomerulosclerosis (FSGS). The divergent electrophoretic profile of HSA was characterized by a shift in the range of pHs between 4.5 and 7.5 with an average variation of free electrophoretic mobility corresponding to loss of 1 positive charge in the pKa protonation range of histidyl residues and should involve domain I of HSA. 'In-gel' determination by maleimide-PEO2-biotin of free SH 34 of domain I showed inaccessibility of the dye at this site in pathological HSA and alkylation with the same complex induced N-A transition in normal HSA. Potential binders of free imidazoles such as Ca++ and/or of SH 34 such as NO were excluded on the basis of direct titration and studies on binding stimulation. This is the first report describing a transition of HSA directly 'in vivo', and the utilization of electrophoretic titration curves was critical to this purpose. This transition appears to be specific to FSGS and is unrelated to the nephrotic syndrome, Ca++ and NO binding. Spectroscopic analysis will elucidate the structural implication.

Rare functional variants of podocin (NPHS2) promoter in patients with nephrotic syndrome.

Podocin (NPHS2) is a component of the glomerular slit-diaphragm, with major regulatory functions in renal permeability of proteins. Loss of podocin and decrease in resynthesis may influence the outcome of proteinuric renal disease such as segmental glomerulosclerosis (FSGS), and promoter functionality plays a key role in this process. NPHS2 promoter variants with functional activity may be a part of the problem of podocin resynthesis. We sequenced NPHS2 promoter region from -628 to ATG in a large cohort of 260 nephrotic patients (161 with FSGS) who were presenting proteinuria from moderate to severe and were receiving or had received modular therapies according to their sensitivity to steroids and other immune modulators. Three sequence variants (-236C>T, -52C>G, -26C>G) were identified in our study population that gave an allele frequency below 1% (5 patients out of 520 alleles). Functional implications were shown for each variants that were most evident for -52C>G and -26C>G (-50% of luciferase expression compared to the wild-type sequence, p < 0.01). Consensus analysis for homology of the -52 region with regulatory factors revealed homology for USF1 and the sum of experiments with gel retardation and with cells silenced for USF1 confirmed that this factor regulates NPHS2 expression at this site. In conclusion, three functional variants in NPHS2 promoter have been identified in a large cohort of patients with nephrotic syndrome and FSGS that have a frequency <1%. One of these (i.e., -52C>G) is associated with a poor clinical outcome and evolution to end-stage renal failure. USF1 was identified as the transcriptional factor regulating NPHS2 at this site. Even if not sufficient to cause FSGS per se, these variants could represent modifiers for severity and/or progression of the disease.

A prospective multicentre study of the nutritional status in children on chronic peritoneal dialysis.

The anthropometry-bioimpedance analysis-nutrition (ABN) score is a recently proposed objective method of assessing malnutrition in children on chronic peritoneal dialysis (CPD) that uses nine parameters based on anthropometry, skinfold thickness and bioimpedance analysis. The aim of this prospective, cross-sectional study was to apply it to children treated with CPD in seven Italian paediatric nephrology centres, with a score of < 10.33 (the 3rd percentile in a population of 264 healthy children) classifying the children as malnourished. The other considered parameters were age, age at the start of dialysis and duration of dialysis; serum haemoglobin, urea, creatinine, total protein, albumin, transferrin, bicarbonate and C-reactive protein; residual urine output; urinary and peritoneal creatinine clearance; and daily protein and energy intake. The study enrolled 43 patients (mean age 10.2 +/- 4.2 years), 21 of whom (48.8%) had an ABN score of < 10.33: 15 with mild, five with moderate, and one with severe malnutrition. The malnourished patients started CPD at a younger age (P < 0.05) and had a longer duration of dialysis (P < 0.01), and a significant worsening in nutritional status was observed in those treated for more than 12 months of dialysis; they also had significantly lower serum albumin, creatinine and haemoglobin levels. In conclusion, protein-calorie malnutrition is common in children receiving CPD. A younger age at the start of dialysis and a longer duration of treatment are clear risk factors, and counterbalance the long-term viability of CPD in paediatric age.

Discordant evolution of nephrotic syndrome in mono- and dizygotic twins.

Twins represent a powerful resource for revealing multifactorial mechanisms in human diseases. Few reports are available on nephrotic syndrome in twins, and most furnish only a partial description of genetic identity based on human leukocyte antigens (HLA) analysis. We describe two pairs of mono and dizygotic twins with nephrotic syndrome who presented discordant outcomes in terms of length and required therapies. In one case, evolution to focal glomerulosclerosis was also documented. The basic molecular work-up included analysis of concordance based on 10 polymorphic markers (D3S1358, vVA, FGA, amelogenin, D8S1179, D21S11, D18S51, D5S818, D13S317, D7S820) and exclusion of the major slit-diaphragm gene mutation (NPHS2, CD2AP, WT1) causing nephrotic syndrome. To our knowledge, this is the first description of long-term outcome in mono- and dizygotic twins with proven genetic concordance. Discordant outcomes indicate a major influence of environmental and/or epigenetic multifactorial mechanisms on persistence and evolution of the disease to focal-segmental glomerulosclerosis.

Impact of pretransplant dialysis on early graft function in pediatric kidney recipients.

Delayed graft function (DGF) is a frequent complication of kidney transplantation (KT) that may affect both short- and long-term graft outcome. It has been reported that pretransplantation peritoneal dialysis was correlated with a better recovery of graft function than hemodialysis in adult kidney recipients. However, the effect of pretransplantation dialysis mode (PDM) seemed to be unclear on the early outcome of KT in pediatric recipients. In this study, the potential impact of PDM on early graft function was evaluated in 174 pediatric patients who underwent KT by using cadaveric donors. The primary outcome parameter was the time to reach a serum creatinine (SCr) level 50% of the pretransplantation value [T(1/2(SCr))], while DGF was defined as a T(1/2(SCr)) >3 days after KT (n = 40). By stratifying kidney recipients for normal function graft or DGF, this latter group showed a significantly higher body weight (BW) on the day of KT (P = 0.014), body surface area (BSA) (P = 0.005), warm ischemia time (WIT) (P = 0.022), early SCr on the day 1 after KT (P < 0.001), and T(1/2(SCr)) (P < 0.001), whereas lower urine volume (UV) collected in the first 24 h after KT (P < 0.001) and fluid load (P < 0.001) occurred. Univariate exponential correlation that was carried out between T(1/2(SCr)) and all the other variables had shown a better value than the linear correlation for BW (R(2) = 0.28 vs. R(2) = 0.04), BSA (R(2) = 0.29 vs. R(2) = 0.03), and SCr (R(2) = 0.51 vs. R(2) = 0.28). In a multivariate regression analysis performed by entering T(1/2(SCr)) as dependent variable and following a forward stepwise method, cold ischemia time (CIT) (P = 0.027) but not PDM (P = 0.195) reached significance. In a Cox regression analysis carried out with T(1/2(SCr)) as dependent variable, neither CIT nor PDM gained significance. This study suggests that PDM does not affect early graft function in pediatric kidney recipients.

One-year angiotensin-converting enzyme inhibition plus mycophenolate mofetil immunosuppression in the course of early IgA nephropathy: a multicenter, randomised, controlled study.

Angiotensin converting-enzyme inhibition (ACEI) is a widely accepted treatment during established renal diseases and beneficial effects have also been reported in IgA nephropathy (IgAN). Immunosuppression with myco-phenolate mofetil (MMF) has recently been introduced in the treatment of immune-mediated renal diseases showing promising results. Preliminary clinical reports are also suggestive that MMF is effective in severe forms of IgAN. We propose a randomised prospective trial aimed to compare long-term renal survival of early IgAN in the course of ACEI therapy with or without MMF immunosuppression.

Pharmacokinetic of cyclosporine microemulsion in pediatric kidney recipients receiving A quadruple immunosuppressive regimen: the value of C2 blood levels.

BACKGROUND: The management of cyclosporine therapy in pediatric kidney-transplant recipients is largely based on single center's experience rather than on a univocal pharmacokinetic approach based on therapeutic drug monitoring. A prospective multicenter trial was designed to address the question whether C2 blood level monitoring of cyclosporine microemulsion therapy is feasible in the pediatric setting. METHODS: Sixty-four pediatric kidney-transplant recipients receiving a triple immunosuppressive regimen based on cyclosporine microemulsion had their cyclosporine dose adjusted to the same protocol-defined C2 targets from the time of the transplant until 2 years posttransplant. The interim analyses after 1 year of enrollment is presented in this study. RESULTS: One-year patient and graft survival were 100% and 94.8%, respectively. One-year rejection rate was 15%. C2 management of cyclosporine did not affect graft function: 1-year serum creatinine and glomerular filtration rate were 1.3+/-1 mg/mL and 71.2+/-20 mL/min/1.73 m2, respectively. C2 was the best single-point predictor of the area under the concentration curve throughout the entire follow-up, with a mean coefficient of correlation of 0.97+/-0.01. CONCLUSIONS: C2 management of cyclosporine microemulsion therapy is effective and safe in pediatric kidney-transplant recipients given a combined immunosuppressive treatment.