Interleukin 17 acts in synergy with B cell-activating factor to influence B cell biology and the pathophysiology of systemic lupus erythematosus

Studies have suggested involvement of interleukin 17 (IL-17) in autoimmune diseases, although its effect on B cell biology has not been clearly established. Here we demonstrate that IL-17 alone or in combination with B cell-activating factor controlled the survival and proliferation of human B cells and their differentiation into immunoglobulin-secreting cells. This effect was mediated mainly through the nuclear factor-kappaB-regulated transcription factor Twist-1. In support of the relevance of our observations and the potential involvement of IL-17 in B cell biology, we found that the serum of patients with systemic lupus erythematosus had higher concentrations of IL-17 than did the serum of healthy people and that IL-17 abundance correlated with the disease severity of systemic lupus erythematosus.

Measurement of bone mineral content of the lumbar spine by dual energy x-ray absorptiometry in normal children: correlations with growth parameters

The bone mineral density (BMD) of the lumbar spine (L1-L4) was measured by dual energy x-ray absorptiometry (Hologic QDR 1000) in 135 healthy caucasian children, aged 1-15 yr, and values were correlated with age, height, weight, body surface, bone age, pubertal status, calcium intake, vitamin D supplementation, and serum bone gla protein. BMD increased with age in children of both sexes (r = 0.88; P less than 0.001) from 0.446 +/- 0.048 g/cm2 at 1 yr to 0.625 +/- 0.068 g/cm2 at 10 yr and 0.891 +/- 0.123 g/cm2 at 15 yr of age. The increase was steeper at the time of puberty, reaching values above 0.80 g/cm2 after puberty was achieved. There were no significant differences between boys and girls, except at the age of 12 yr when BMD was higher in girls than in boys (P = 0.007), probably because of the earlier onset of puberty in females. BMD was also highly correlated with height, weight, body surface, and bone age. BMD was not correlated with calcium intake when age was held constant, nor with vitamin D supplementation. Serum bone gla protein showed a steady increase during childhood, with peak values at 11-12 yr of age, and was weakly but significantly correlated with BMD (r = 0.27; P = 0.007). Because of low irradiation exposure, rapid scanning, and high precision, dual energy x-ray absorptiometry is a noninvasive method which is well adapted to the child. It should be helpful in the investigation and follow-up of children with diseases impairing bone metabolism.

Human laminin beta2 deficiency causes congenital nephrosis with mesangial sclerosis and distinct eye abnormalities

Congenital nephrotic syndrome (CNS) is clinically and genetically heterogeneous, with mutations in WT1, NPHS1 and NPHS2 accounting for part of cases. We recently delineated a new autosomal recessive entity comprising CNS with diffuse mesangial sclerosis and distinct ocular anomalies with microcoria as the leading clinical feature (Pierson syndrome). On the basis of homozygosity mapping to markers on chromosome 3p14-p22, we identified homozygous or compound heterozygous mutations of LAMB2 in patients from five unrelated families. Most disease-associated alleles were truncating mutations. Using immunohistochemistry and western blotting we could demonstrate that the respective LAMB2 mutations lead to loss of laminin beta2 expression in kidney and other tissues studied. Laminin beta2 is known to be abundantly expressed in the glomerular basement membrane (GBM) where it is thought to play a key role in anchoring as well as differentiation of podocyte foot processes. Lamb2 knockout mice were reported to exhibit congenital nephrosis in association with anomalies of retina and neuromuscular junctions. By studying ocular laminin beta2 expression in unaffected controls, we detected the strongest expression in the intraocular muscles corresponding well to the characteristic hypoplasia of ciliary and pupillary muscles observed in patients. Moreover, we present first clinical evidence of severe impairment of vision and neurodevelopment due to LAMB2 defects. Our current data suggest that human laminin beta2 deficiency is consistently and specifically associated with this particular oculorenal syndrome. In addition, components of the molecular interface between GBM and podocyte foot processes come in the focus as potential candidates for isolated and syndromic CNS.

Lumasiran, an RNAi Therapeutic for Primary Hyperoxaluria Type 1

BACKGROUND

Primary hyperoxaluria type 1 (PH1) is a rare genetic disease caused by hepatic overproduction of oxalate that leads to kidney stones, nephrocalcinosis, kidney failure, and systemic oxalosis. Lumasiran, an investigational RNA interference (RNAi) therapeutic agent, reduces hepatic oxalate production by targeting glycolate oxidase.

METHODS

In this double-blind, phase 3 trial, we randomly assigned (in a 2:1 ratio) patients with PH1 who were 6 years of age or older to receive subcutaneous lumasiran or placebo for 6 months (with doses given at baseline and at months 1, 2, 3, and 6). The primary end point was the percent change in 24-hour urinary oxalate excretion from baseline to month 6 (mean percent change across months 3 through 6). Secondary end points included the percent change in the plasma oxalate level from baseline to month 6 (mean percent change across months 3 through 6) and the percentage of patients with 24-hour urinary oxalate excretion no higher than 1.5 times the upper limit of the normal range at month 6.

RESULTS

A total of 39 patients underwent randomization; 26 were assigned to the lumasiran group and 13 to the placebo group. The least-squares mean difference in the change in 24-hour urinary oxalate excretion (lumasiran minus placebo) was -53.5 percentage points (P<0.001), with a reduction in the lumasiran group of 65.4% and an effect seen as early as month 1. The between-group differences for all hierarchically tested secondary end points were significant. The difference in the percent change in the plasma oxalate level (lumasiran minus placebo) was -39.5 percentage points (P<0.001). In the lumasiran group, 84% of patients had 24-hour urinary oxalate excretion no higher than 1.5 times the upper limit of the normal range at month 6, as compared with 0% in the placebo group (P<0.001). Mild, transient injection-site reactions were reported in 38% of lumasiran-treated patients.

CONCLUSIONS

Lumasiran reduced urinary oxalate excretion, the cause of progressive kidney failure in PH1. The majority of patients who received lumasiran had normal or near-normal levels after 6 months of treatment. (Funded by Alnylam Pharmaceuticals; ILLUMINATE-A ClinicalTrials.gov number, NCT03681184.).

ADCK4 mutations promote steroid-resistant nephrotic syndrome through CoQ10 biosynthesis disruption

Identification of single-gene causes of steroid-resistant nephrotic syndrome (SRNS) has furthered the understanding of the pathogenesis of this disease. Here, using a combination of homozygosity mapping and whole human exome resequencing, we identified mutations in the aarF domain containing kinase 4 (ADCK4) gene in 15 individuals with SRNS from 8 unrelated families. ADCK4 was highly similar to ADCK3, which has been shown to participate in coenzyme Q10 (CoQ10) biosynthesis. Mutations in ADCK4 resulted in reduced CoQ10 levels and reduced mitochondrial respiratory enzyme activity in cells isolated from individuals with SRNS and transformed lymphoblasts. Knockdown of adck4 in zebrafish and Drosophila recapitulated nephrotic syndrome-associated phenotypes. Furthermore, ADCK4 was expressed in glomerular podocytes and partially localized to podocyte mitochondria and foot processes in rat kidneys and cultured human podocytes. In human podocytes, ADCK4 interacted with members of the CoQ10 biosynthesis pathway, including COQ6, which has been linked with SRNS and COQ7. Knockdown of ADCK4 in podocytes resulted in decreased migration, which was reversed by CoQ10 addition. Interestingly, a patient with SRNS with a homozygous ADCK4 frameshift mutation had partial remission following CoQ10 treatment. These data indicate that individuals with SRNS with mutations in ADCK4 or other genes that participate in CoQ10 biosynthesis may be treatable with CoQ10.

Primary hyperoxaluria Type 1: indications for screening and guidance for diagnosis and treatment

Primary hyperoxaluria Type 1 is a rare autosomal recessive inborn error of glyoxylate metabolism, caused by a deficiency of the liver-specific enzyme alanine:glyoxylate aminotransferase. The disorder results in overproduction and excessive urinary excretion of oxalate, causing recurrent urolithiasis and nephrocalcinosis. As glomerular filtration rate declines due to progressive renal involvement, oxalate accumulates leading to systemic oxalosis. The diagnosis is based on clinical and sonographic findings, urine oxalate assessment, enzymology and/or DNA analysis. Early initiation of conservative treatment (high fluid intake, pyridoxine, inhibitors of calcium oxalate crystallization) aims at maintaining renal function. In chronic kidney disease Stages 4 and 5, the best outcomes to date were achieved with combined liver-kidney transplantation.

European Renal Best Practice Guideline on kidney donor and recipient evaluation and perioperative care

The European Best Practice Guideline group (EBPG) issued guidelines on the evaluation and selection of kidney donor and kidney transplant candidates, as well as post-transplant recipient care, in the year 2000 and 2002. The new European Renal Best Practice board decided in 2009 that these guidelines needed updating. In order to avoid duplication of efforts with kidney disease improving global outcomes, which published in 2009 clinical practice guidelines on the post-transplant care of kidney transplant recipients, we did not address these issues in the present guidelines.The guideline was developed following a rigorous methodological approach: (i) identification of clinical questions, (ii) prioritization of questions, (iii) systematic literature review and critical appraisal of available evidence and (iv) formulation of recommendations and grading according to Grades of Recommendation Assessment, Development, and Evaluation (GRADE). The strength of each recommendation is rated 1 or 2, with 1 being a 'We recommend' statement, and 2 being a 'We suggest' statement. In addition, each statement is assigned an overall grade for the quality of evidence: A (high), B (moderate), C (low) or D (very low). The guideline makes recommendations for the evaluation of the kidney transplant candidate as well as the potential deceased and living donor, the immunological work-up of kidney donors and recipients and perioperative recipient care.All together, the work group issued 112 statements. There were 51 (45%) recommendations graded '1', 18 (16%) were graded '2' and 43 (38%) statements were not graded. There were 0 (0%) recommendations graded '1A', 15 (13%) were '1B', 19 (17%) '1C' and 17 (15%) '1D'. None (0%) were graded '2A', 1 (0.9%) was '2B', 8 (7%) were '2C' and 9 (8%) '2D'. Limitations of the evidence, especially the lack of definitive clinical outcome trials, are discussed and suggestions are provided for future research.We present here the complete recommendations about the evaluation of the kidney transplant candidate as well as the potential deceased and living donor, the immunological work-up of kidney donors and recipients and the perioperative recipient care. We hope that this document will help caregivers to improve the quality of care they deliver to patients. The full version with methods, rationale and references is published in Nephrol Dial Transplant (2013) 28: i1-i71; doi: 10.1093/ndt/gft218 and can be downloaded freely from http://www.oxfordjournals.org/our_journals/ndt/era_edta.html.

Mutations in the human laminin beta2 (LAMB2) gene and the associated phenotypic spectrum

Mutations of LAMB2 typically cause autosomal recessive Pierson syndrome, a disorder characterized by congenital nephrotic syndrome, ocular and neurologic abnormalities, but may occasionally be associated with milder or oligosymptomatic disease variants. LAMB2 encodes the basement membrane protein laminin beta2, which is incorporated in specific heterotrimeric laminin isoforms and has an expression pattern corresponding to the pattern of organ manifestations in Pierson syndrome. Herein we review all previously reported and several novel LAMB2 mutations in relation to the associated phenotype in patients from 39 unrelated families. The majority of disease-causing LAMB2 mutations are truncating, consistent with the hypothesis that loss of laminin beta2 function is the molecular basis of Pierson syndrome. Although truncating mutations are distributed across the entire gene, missense mutations are clearly clustered in the N-terminal LN domain, which is important for intermolecular interactions. There is an association of missense mutations and small in frame deletions with a higher mean age at onset of renal disease and with absence of neurologic abnormalities, thus suggesting that at least some of these may represent hypomorphic alleles. Nevertheless, genotype alone does not appear to explain the full range of clinical variability, and therefore hitherto unidentified modifiers are likely to exist.

IgACE: A Placebo-Controlled, Randomized Trial of Angiotensin-Converting Enzyme Inhibitors in Children and Young People with IgA Nephropathy and Moderate Proteinuria

This European Community Biomedicine and Health Research-supported, multicenter, randomized, placebo-controlled, double-blind trial investigated the effect of an angiotensin-converting enzyme inhibitor (ACE-I) in children and young people with IgA nephropathy (IgAN), moderate proteinuria (>1 and <3.5 g/d per 1.73 m(2)) and creatinine clearance (CrCl) >50 ml/min per 1.73 m(2). Sixty-six patients who were 20.5 yr of age (range 9 to 35 yr), were randomly assigned to Benazepril 0.2 mg/kg per d (ACE-I) or placebo and were followed for a median of 38 mo. The primary outcome was the progression of kidney disease, defined as >30% decrease of CrCl; secondary outcomes were (1) a composite end point of >30% decrease of CrCl or worsening of proteinuria until > or =3.5 g/d per 1.73 m(2) and (2) proteinuria partial remission (<0.5 g/d per 1.73 m(2)) or total remission (<160 mg/d per 1.73 m(2)) for >6 mo. Analysis was by intention to treat. A single patient (3.1%) in the ACE-I group and five (14.7%) in the placebo group showed a worsening of CrCl >30%. The composite end point of >30% decrease of CrCl or worsening of proteinuria until nephrotic range was reached by one (3.1%) of 32 patients in the ACE-I group, and nine (26.5%) of 34 in the placebo group; the difference was significant (log-rank P = 0.035). A stable, partial remission of proteinuria was observed in 13 (40.6%) of 32 patients in the ACE-I group versus three (8.8%) of 34 in the placebo group (log-rank P = 0.033), with total remission in 12.5% of ACE-I-treated patients and in none in the placebo group (log-rank P = 0.029). The multivariate Cox analysis showed that treatment with ACE-I was the independent predictor of prognosis; no influence on the composite end point was found for gender, age, baseline CrCl, systolic or diastolic BP, mean arterial pressure, or proteinuria.

Cysteamine therapy delays the progression of nephropathic cystinosis in late adolescents and adults

Nephropathic cystinosis is a multisystem autosomal recessive disease caused by cystine accumulation, which is usually treated by oral cysteamine. In order to determine long-term effects of this therapy, we enrolled 86 adult patients (mean age 26.7 years) diagnosed with nephropathic cystinosis, 75 of whom received cysteamine. Therapy was initiated at a mean age of 9.9 years with a mean duration of 17.4 years. By last follow-up, 78 patients had end-stage renal disease (mean age 11.1 years), 62 had hypothyroidism (mean age 13.4), 48 developed diabetes (mean age 17.1 years), and 32 had neuromuscular disorders (mean age 23.3 years). Initiating cysteamine therapy before 5 years of age significantly decreased the incidence and delayed the onset of end-stage renal disease, and significantly delayed the onset of hypothyroidism, diabetes, and neuromuscular disorders. The development of diabetes and hypothyroidism was still significantly delayed, however, in patients in whom therapy was initiated after 5 years of age, compared with untreated patients. The life expectancy was significantly improved in cysteamine-treated versus untreated patients. Thus, cysteamine decreases and delays the onset of complications and improves life expectancy in cystinosis. Hence, cysteamine therapy should be introduced as early as possible during childhood and maintained lifelong.

A Cluster of Mutations in the UMOD Gene Causes Familial Juvenile Hyperuricemic Nephropathy with Abnormal Expression of Uromodulin

ABSTRACT. Familial juvenile hyperuricemic nephropathy (FJHN [MIM 162000]) is an autosomal-dominant disorder characterized by abnormal tubular handling of urate and late development of chronic interstitial nephritis leading to progressive renal failure. A locus for FJHN was previously identified on chromosome 16p12 close to the MCKD2 locus, which is responsible for a variety of autosomal-dominant medullary cystic kidney disease (MCKD2). UMOD, the gene encoding the Tamm-Horsfall/uromodulin protein, maps within the FJHN/MCKD2 critical region. Mutations in UMOD were recently reported in nine families with FJHN/MCKD2 disease. A mutation in UMOD has been identified in 11 FJHN families (10 missense and one in-frame deletion)—10 of which are novel—clustering in the highly conserved exon 4. The consequences of UMOD mutations on uromodulin expression were investigated in urine samples and renal biopsies from nine patients in four families. There was a markedly increased expression of uromodulin in a cluster of tubule profiles, suggesting an accumulation of the protein in tubular cells. Consistent with this observation, urinary excretion of wild-type uromodulin was significantly decreased. The latter findings were not observed in patients with FJHN without UMOD mutations. In conclusion, this study points to a mutation clustering in exon 4 of UMOD as a major genetic defect in FJHN. Mutations in UMOD may critically affect the function of uromodulin, resulting in abnormal accumulation within tubular cells and reduced urinary excretion. E-mail: Dahan@gmed.ucl.ac.be

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.

Nephropathic cystinosis: an international consensus document

Cystinosis is caused by mutations in the CTNS gene (17p13.2), which encodes for a lysosomal cystine/proton symporter termed cystinosin. It is the most common cause of inherited renal Fanconi syndrome in young children. Because of its rarity, the diagnosis and specific treatment of cystinosis are frequently delayed, which has a significant impact on the overall prognosis. In this document, we have summarized expert opinions on several aspects of the disease to improve knowledge and provide guidance for diagnosis and treatment.

Epidemiology of primary hyperoxaluria type 1. Société de Néphrologie and the Société de Néphrologie Pédiatrique

Primary hyperoxaluria type 1 (PH1) always leads to oxalate accumulation throughout the body (oxalosis). Currently available epidemiological data only concern patients with end-stage kidney disease requiring renal replacement therapy (RRT). French nephrologists have been questioned about PH1 patients who were under their care between 1988 and 1992. Exhaustive answers were obtained and 90 cases of PH1 were collected. The average prevalence rate of PH1 was 1.05/10(6) and its average incidence rate was 0.12/10(6)/year. The median age at onset was 5 years (0-63) and initial symptoms involved the urinary tract in 82% of the cases. Half the patients were younger than 10 years at the time of diagnosis on the basis of urine oxalate (89%) +/- urine glycolate (43%) +/- plasma oxalate (71%) +/- hepatic alanine:glyoxylate amino-transferase activity (48%). At the time of the survey, 36% of patients were on a conservative treatment, 37% were transplanted and 27% were on maintenance haemodialysis; the crude mortality rate was 19% (median age 36 years). Patients on dialysis started RRT at a median age of 25 years. Transplanted patients received their first transplant at a median age of 29.5 years; among those patients with more than 1 year follow-up, 15 received an isolated kidney transplant (one success), one had a isolated liver transplant (one success) and 10 combined liver-kidney transplant (eight successes). These data confirm the rarity of PH1 together with its poor prognosis; as shown in the European experience, early combined liver-kidney transplantation seems to be the best therapeutic proposal.

Protein kinase cδ deficiency causes mendelian systemic lupus erythematosus with B cell-defective apoptosis and hyperproliferation

OBJECTIVE

Systemic lupus erythematosus (SLE) is a prototype autoimmune disease that is assumed to occur via a complex interplay of environmental and genetic factors. Rare causes of monogenic SLE have been described, providing unique insights into fundamental mechanisms of immune tolerance. The aim of this study was to identify the cause of an autosomal-recessive form of SLE.

METHODS

We studied 3 siblings with juvenile-onset SLE from 1 consanguineous kindred and used next-generation sequencing to identify mutations in the disease-associated gene. We performed extensive biochemical, immunologic, and functional assays to assess the impact of the identified mutations on B cell biology.

RESULTS

We identified a homozygous missense mutation in PRKCD, encoding protein kinase δ (PKCδ), in all 3 affected siblings. Mutation of PRKCD resulted in reduced expression and activity of the encoded protein PKCδ (involved in the deletion of autoreactive B cells), leading to resistance to B cell receptor- and calcium-dependent apoptosis and increased B cell proliferation. Thus, as for mice deficient in PKCδ, which exhibit an SLE phenotype and B cell expansion, we observed an increased number of immature B cells in the affected family members and a developmental shift toward naive B cells with an immature phenotype.

CONCLUSION

Our findings indicate that PKCδ is crucial in regulating B cell tolerance and preventing self-reactivity in humans, and that PKCδ deficiency represents a novel genetic defect of apoptosis leading to SLE.

Paraneoplastic glomerular diseases and malignancies

Paraneoplastic glomerulopathies are rare manifestations of neoplastic disease to be distinguished from iatrogenic renal damage. Solid tumors are preferentially associated with membranous nephropathy, whereas Hodgkin's lymphomas are associated with minimal change disease. The most common neoplasia associated with paraneoplastic glomerular disease are carcinomas of the lung and of the gastrointestinal tract. Nephrotic syndrome is the most frequent presentation of paraneoplastic glomerulopathy and the most critical glomerular disease regarding prognosis and patient care. Renal biopsy is recommended in patients with glomerular proteinuria or nephrotic syndrome and cancer, depending on life expectancy and therapeutic options. The primary treatment must be directed at the cancer in all cases. Symptomatic treatment of the nephrotic syndrome with diuretics and ACE inhibitors is justified. Prevention of nephrotic syndrome complications, i.e. thromboses and infections, should also be addressed and systematic regular renal follow-up is warranted. All treatments should be regularly reviewed to avoid toxicity, associated renal function loss or low albumin levels for patients receiving albumin-binding drugs. Epidemiologic studies have low evidence-based value. There is no widely accepted experimental model of the association of glomerulopathy and cancer. Thus, epidemiologic and mechanistic studies are needed to determine the true prevalence of paraneoplastic glomerulopathies and investigate new pathophysiologic approaches.

Long-term outcome of idiopathic steroid-resistant nephrotic syndrome: a multicenter study

Long-term outcome of idiopathic steroid-resistant nephrotic syndrome was retrospectively studied in 78 children in eight centers for the past 20 years. Median age at onset was 4.4 years (1.1-15.0 years) and the gender ratio was 1.4. Median follow-up period was 7.7 years (1.0-19.7 years). The disease in 45 patients (58%) was initially not steroid-responsive and in 33 (42%) it was later non-responsive. The main therapeutic strategies included administration of ciclosporine (CsA) alone (n = 29; 37%) and CsA + mycophenolate mofetil (n = 18; 23%). Actuarial patient survival rate after 15 years was 97%. Renal survival rate after 5 years, 10 years and 15 years was 75%, 58% and 53%, respectively. An age at onset of nephrotic syndrome (NS) > 10 years was the only independent predictor of end-stage renal disease (ESRD) in a multivariate analysis using a Cox regression model (P < 0.001). Twenty patients (26%) received transplants; ten showed recurrence of the NS: seven within 2 days, one within 2 weeks, and two within 3-5 months. Seven patients lost their grafts, four from recurrence. Owing to better management, kidney survival in idiopathic steroid-resistant nephrotic syndrome (SRNS) has improved during the past 20 years. Further prospective controlled trials will delineate the potential benefit of new immunosuppressive treatment.

A randomized trial to assess the impact of early steroid withdrawal on growth in pediatric renal transplantation: the TWIST study

Minimizing steroid exposure in pediatric renal transplant recipients can improve linear growth and reduce metabolic disorders. This randomized multicenter study investigated the impact of early steroid withdrawal on mean change in height standard deviation score (SDS) and the safety and efficacy of two immunosuppressive regimens during the first 6 months after transplantation. Children received tacrolimus, MMF, two doses of daclizumab and steroids until day 4 (TAC/MMF/DAC, n=98) or tacrolimus, MMF and standard-dose steroids (TAC/MMF/STR, n=98). Mean change in height SDS was 0.16 +/- 0.32 with TAC/MMF/DAC and 0.03 +/- 0.32 with TAC/MMF/STR. The mean treatment group difference was 0.13 (p < 0.005 [95% CI 0.04-0.22]), 0.21 in prepubertal (p = 0.009 [95% CI 0.05-0.36]) and 0.05 in pubertal children (p = ns). Frequency of biopsy-proven acute rejection was 10.2%, TAC/MMF/DAC, and 7.1%, TAC/MMF/STR. Patient and graft survival and renal function were similar. Significantly greater reductions in total cholesterol and triglycerides but significantly higher incidences of infection and anemia were found with TAC/MMF/DAC (p < 0.05 all comparisons). Early steroid withdrawal significantly aided growth at 6 months more so in prepubertal than pubertal children. This was accompanied by significantly better lipid and glucose metabolism profiles without increases in graft rejection or loss.

A new equation to estimate the glomerular filtration rate in children, adolescents and young adults

BACKGROUND

A new estimated glomerular filtration rate (eGFR) equation, designed for isotope dilution mass spectrometry-standardized serum creatinine (Scr), is presented for use in children, adolescent boys and girls and young adults.

METHODS

The new equation, eGFR = 107.3/(Scr/Q), is based on the concept of normalized Scr: Q is the normalization value and is considered as the Scr concentration for the average healthy child, adolescent or young adult of a specific height (L) and is modeled as a height-dependent polynomial of the fourth degree.

RESULTS

The well-known Schwartz equation [eGFR = kL/Scr, k = 0.413 (Schwartz) or k = 0.373 (Schwartz-Lyon)] for children between 1 and 14 years can be seen as a special case of the new equation for which the Q-polynomial is simplified to a linear equation: Q = 0.0035 × L (cm). The new eGFR equation has been validated in a data set of n = 750 children, adolescents and young adults aged 10-25, against the true GFR (inulin method), and outperforms the selected (but most used) creatinine-based eGFR equations for children, mainly in the healthy GFR region.

CONCLUSIONS

The new Q(height)-eGFR equation serves as an excellent screening tool for kidney disease in 1-25-year-old children, adolescents and young adults.

Genotype-phenotype correlation in primary hyperoxaluria type 1: the p.Gly170Arg AGXT mutation is associated with a better outcome

We sought to ascertain the long-term outcome and genotype-phenotype correlations available for primary hyperoxaluria type 1 in a large retrospective cohort study. We examined the clinical history of 155 patients (129 families primarily from Western Europe, North Africa, or the Middle East) as well as the enzymatic or genetic diagnosis. The median age at first symptom was 4 years, and at diagnosis 7.7 years, at which time 43% had reached end-stage renal disease. Presentations included: (1) early nephrocalcinosis and infantile renal failure, (2) recurrent urolithiasis and progressive renal failure diagnosed during childhood, (3) late onset with occasional stone passage diagnosed in adulthood, (4) diagnosis occurring on post-transplantation recurrence, and (5) family screening. The cumulative patient survival was 95, 86, and 74% at ages 10, 30, and 50 years, respectively, with the cumulative renal survival of 81, 59, 41, and 10% at ages 10, 20, 30, and 50 years, respectively; 72 patients had undergone a total of 97 transplantations. Among the 136 patients with DNA analysis, the most common mutation was p.Gly170Arg (allelic frequency 21.5%), with a median age at end-stage renal disease of 47 years for homozygotes, 35 years for heterozygotes, and 21 years for other mutations. Our results underscore the severe prognosis of primary hyperoxaluria type 1 and the necessity for early diagnosis and treatment, as well as confirm a better prognosis of the p.Gly170Arg mutation.

Phenotype-genotype correlation in antenatal and neonatal variants of Bartter syndrome

BACKGROUND

Ante/neonatal Bartter syndrome (BS) is a hereditary salt-losing tubulopathy due to mutations in genes encoding proteins involved in NaCl reabsorption in the thick ascending limb of Henle's loop. Our aim was to study the frequency, clinical characteristics and outcome of each genetic subtype.

METHODS

Charts of 42 children with mutations in KCNJ1 (n = 19), SLC12A1 (n = 13) CLCNKB (n = 6) or BSND (n = 4) were retrospectively analysed. The median follow-up was 8.3 [0.4-18.0] years.

RESULTS

We describe 24 new mutations: 10 in KCNJ1, 11 in SLC12A1 and 3 in CLCNKB. The onset of polyhydramnios, birth term, height and weight were similar for all groups; three patients had no history of polyhydramnios or premature birth and had CLCNKB mutations according to a less severe renal sodium wasting. Contrasting with these data, patients with CLCNKB had the lowest potassium (P = 0.006 versus KCNJ1 and P = 0.034 versus SLC12A1) and chloride plasma concentrations (P = 0.039 versus KCNJ1 and P = 0.024 versus SLC12A1) and the highest bicarbonataemia (P = 0.026 versus KCNJ1 and P = 0.014 versus SLC12A1). Deafness at diagnosis was constant in patients with BSND mutations; transient neonatal hyperkalaemia was present in two-thirds of the children with KCNJ1 mutations. Nephrocalcinosis was constant in KCNJ1 and SLC12A1 but not in BSND and CLCNKB patients. In most cases, water/electrolyte supplementation + indomethacin led to catch-up growth. Three patients developed chronic renal failure: one with KCNJ1 mutations during the second decade of age and two with CLCNKB and BSND mutations and without nephrocalcinosis during the first year of life.

CONCLUSIONS

We confirmed in a large cohort of ante/ neonatal BS that deafness, transient hyperkalaemia and severe hypokalaemic hypochloraemic alkalosis orientate molecular investigations to BSND, KCNJ1 and CLCNKB genes, respectively. Chronic renal failure is a rare event, associated in this cohort with three genotypes and not always associated with nephrocalcinosis.

Efficacy and safety of Oxalobacter formigenes to reduce urinary oxalate in primary hyperoxaluria

BACKGROUND

Primary hyperoxaluria (PH) is a rare genetic disease, in which high urinary oxalate (Uox) cause recurrent kidney stones and/or progressive nephrocalcinosis, often followed by early end-stage renal disease, as well as extremely high plasma oxalate, systemic oxalosis and premature death. Oxalobacter formigenes, an anaerobic oxalate degrading bacterium, naturally colonizes the colon of most humans. Orally administered O. formigenes (Oxabact) was found to significantly reduce urine and plasma oxalate. We aimed to evaluate its effect and safety in a randomized, double-blind, placebo-controlled multicenter study.

METHODS

Oral Oxabact was given to PH patients (>5 years old, Uox > 1.0 mmol/1.73 m(2)/day, glomerular filtration rate (GFR) > 50 mL/min) at nine PH referral sites worldwide. Primary endpoint was the change from baseline in Uox (mmol/1.73 m(2)/day) after 24 weeks of treatment (>20% reduction).

RESULTS

Of the 43 subjects randomized, 42 patients received either placebo (23 subjects) or Oxabact (19 subjects). The change in Uox was <20% and not different between groups (P = 0.616). Ad hoc analysis was performed in 37 patients compliant with medication and urine processing. Change in Uox was -19% in subjects given Oxabact and -10% in placebo, (P = 0.288), but -21 and -7% with Uox expressed as molar creatinine ratio (Ox:Cr, mmol/mol, P = 0.06). Reduction of Ox:Cr was more obvious for patients with higher baseline values (>160 mmol/mol, Oxabact -28%, placebo -6%; P < 0.082). No serious adverse events were reported.

CONCLUSION

Oxabact was safe and well tolerated. However, as no significant change in Uox was seen, further studies to evaluate the efficacy of Oxabact treatment are needed.

Characteristics and outcomes of children with primary oxalosis requiring renal replacement therapy

BACKGROUND AND OBJECTIVES

Primary hyperoxaluria (PH) as a cause of ESRD in children is believed to have poor outcomes. Data on management and outcomes of these children remain scarce.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This study included patients aged <19 years who started renal replacement therapy (RRT) between 1979 and 2009 from 31 countries providing data to a large European registry.

RESULTS

Of 9247 incident patients receiving RRT, 100 patients had PH. PH children were significantly younger than non-PH children at the start of RRT. The median age at RRT of PH children decreased from 9.8 years in 1979-1989 to 1.5 years in 2000-2009. Survival was 86%, 79%, and 76% among PH patients at 1, 3, and 5 years after the start of RRT, compared with 97%, 94%, and 92% in non-PH patients, resulting in a three-fold increased risk of death over non-PH patients. PH and non-PH patient survival improved over time. Sixty-eight PH children received a first kidney (n=13) or liver-kidney transplantation (n=55). Although the comparison was hampered by the lower number of kidney transplantations primarily derived from the earlier era of RRT, kidney graft survival in PH patients was 82%, 79%, and 76% at 1, 3, and 5 years for liver-kidney transplantation and 46%, 28%, and 14% at 1, 3, and 5 years for kidney transplantation alone, compared with 95%, 90%, and 85% in non-PH patients.

CONCLUSIONS

The outcomes of PH children with ESRD are still poorer than in non-PH children but have substantially improved over time.

The influence of glomerular filtration rate and age on fibroblast growth factor 23 serum levels in pediatric chronic kidney disease

BACKGROUND

Fibroblast growth factor 23 (FGF23) is a phosphaturic factor and a suppressor of 1alpha-hydroxylase activity in the kidney. Although its importance in chronic kidney disease (CKD) has been demonstrated in adults, there is little information in pediatric patients.

OBJECTIVES

The aims of this study were: 1) to determine reference values for FGF23 serum levels according to glomerular filtration rate (GFR) (measured by the reference standard, inulin clearance), gender, and age; and 2) to evaluate the effects of different etiologies and treatments on FGF23 serum levels in a prospective single-center cohort of 227 CKD children (119 boys).

RESULTS

Age, body weight, height, and GFR (mean +/- sd) values were: 11.3 +/- 4.1 yr, 37 +/- 16 kg, 140 +/- 20 cm, and 98 +/- 34 ml/min per 1.73 m(2), respectively. Calcium, phosphate, PTH, 25 hydroxyvitamin D, 1,25 dihydroxyvitamin D, C-terminal FGF23, and intact FGF23 (mean +/- sd) levels were: 2.43 +/- 0.11 mmol/liter, 1.41 +/- 0.22 mmol/liter, 41 +/- 23 pg/ml, 24 +/- 10 ng/ml, 152 +/- 72 pmol/liter, 76 +/- 134 relative units/ml, and 44 +/- 37 pg/ml, respectively. There was a wide range of FGF23 serum levels, but FGF23 levels increased when GFR decreased. FGF23 serum levels were not modified by gender, but they increased with age. In univariate analysis, corticosteroid therapy seemed to be associated with increased FGF23 serum levels. A multivariate linear regression analysis found a significant impact of GFR, body mass index, and solid organ transplantation on FGF23 serum levels.

CONCLUSION

Age, GFR, body mass index, and solid organ transplantation seem to influence FGF23 serum levels in a pediatric population. The impact of corticosteroids on FGF23 metabolism should be further investigated; further longitudinal studies will also help to better define the prognostic impact of FGF23 serum levels in pediatric CKD in terms of disease progression, cardiovascular morbidities, and bone disabilities.