[Show abstract][Hide abstract] ABSTRACT: Steroid-resistant nephrotic syndrome (SRNS) is the second most frequent cause of ESRD in the first two decades of life. Effective treatment is lacking. First insights into disease mechanisms came from identification of single-gene causes of SRNS. However, the frequency of single-gene causation and its age distribution in large cohorts are unknown. We performed exon sequencing of NPHS2 and WT1 for 1783 unrelated, international families with SRNS. We then examined all patients by microfluidic multiplex PCR and next-generation sequencing for all 27 genes known to cause SRNS if mutated. We detected a single-gene cause in 29.5% (526 of 1783) of families with SRNS that manifested before 25 years of age. The fraction of families in whom a single-gene cause was identified inversely correlated with age of onset. Within clinically relevant age groups, the fraction of families with detection of the single-gene cause was as follows: onset in the first 3 months of life (69.4%), between 4 and 12 months old (49.7%), between 1 and 6 years old (25.3%), between 7 and 12 years old (17.8%), and between 13 and 18 years old (10.8%). For PLCE1, specific mutations correlated with age of onset. Notably, 1% of individuals carried mutations in genes that function within the coenzyme Q10 biosynthesis pathway, suggesting that SRNS may be treatable in these individuals. Our study results should facilitate molecular genetic diagnostics of SRNS, etiologic classification for therapeutic studies, generation of genotype-phenotype correlations, and the identification of individuals in whom a targeted treatment for SRNS may be available.
Journal of the American Society of Nephrology 06/2015; 26(6):1279-89. · 9.34 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Verbesserte diagnostische Verfahren und die Verfügbarkeit neuer Medikamente haben zu einer Optimierung der Behandlung von Harnwegsinfektionen (HWI) geführt. Aktuell diskutierte Fragen betreffen u. a. Therapiestrategien bei Pyelonephritis im Säuglings- und Kleinkindalter, den Umgang mit der Resistenzentwicklung uropathogener Bakterien, konkurrierende Konzepte der bildgebenden Diagnostik und die Effizienz der antibakteriellen Rezidivprophylaxe. Die kalkulierte antibakterielle Therapie muss sich zunehmend an der jeweils regionalen Resistenzsituation uropathogener Bakterien orientieren. Jenseits des frühen Säuglingsalters ist die orale Applikation geeigneter Antibiotika bei unkomplizierten Pyelonephritiden angemessen. In aktuellen Leitlinien gehört die Sonographie im Säuglings- und Kleinkindalter zur Basisdiagnostik bei fieberhaften HWI. Die Refluxdiagnostik bleibt dagegen denjenigen Kindern vorbehalten, bei denen angesichts klinischer Kriterien oder dem Vorliegen wegweisender sonographischer Auffälligkeiten ein behandungsbedürftiger vesikorenaler Reflux wahrscheinlich ist. Aktuelle Studien belegen die Effizienz einer antibakteriellen Rezidivprophylaxe bei gefährdeten Patienten. Bei Mädchen mit rezidivierenden Zystitiden gewinnen die pathogenetische Rolle von Blasen- und Darmfunktionsstörungen und der Einsatz der Urotherapie praktische Relevanz. Abstract Improved diagnostic procedures as well as the availability of novel drugs have led to an optimization in the treatment of urinary tract infections in infancy and childhood. Current important issues under discussion are the therapeutic strategies for pyelonephritis in infancy and early childhood, how to deal with resistance development of uropathogenic bacteria, competing concepts of diagnostic imaging and the efficiency of antibacterial prophylaxis for recurrence. Increasingly, calculated antibacterial therapy must be oriented to the respective regional resistance situation of uropathogenic bacteria. Beyond early infancy, oral administration of suitable antibiotics is appropriate in uncomplicated cases of pyelonephritis. According to the current guidelines, sonography in infancy and early childhood is part of the basic diagnostic regimen for febrile urinary tract infections. Reflux diagnostics, however, remain reserved for children in whom a vesicorenal reflux is likely in view of clinical criteria or the existence of conclusive sonographic abnormalities. Recent studies have proven the efficiency of prophylaxis for antibacterial recurrence in patients at risk. In girls presenting with recurrent cystitis, the pathogenic role of functional bladder or bowel disorders as well as the use of urotherapy are gaining practical relevance.
[Show abstract][Hide abstract] ABSTRACT: The treatment of children and adolescents with meningomyelocele has experienced a clear change in the last 30 years. The establishment of pharmacotherapy, clean intermittent catheterization (CIC) and infection prophylaxis have improved the prognosis for patients and have led to new therapeutic strategies. The interdisciplinary cooperation between neonatologists, neurosurgeons, pediatric neurologists, pediatric urologists, pediatric nephrologists, pediatric orthopedists and pediatric surgeons leads to optimization of individualized therapy. These guidelines present definitions and classifications, investigations and timing which are described in detail. The conservative and operative therapy options for neurogenic bladder function disorders are described and discussed with reference to the current literature. The brief overview provides in each case assistance for the treating physician in the care of this patient group and facilitates the interdisciplinary cooperation.
Der Urologe 02/2015; 54(2):239-53. DOI:10.1007/s00120-013-3403-2 · 0.44 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The aim of this study was to evaluate the long-term prognosis of children with hemolytic uremic syndrome (HUS).
Over a 6-year period, 619 pediatric patients with the clinical diagnosis of HUS were registered in Austria and Germany, and a subset (n = 274) was prospectively followed up for 5 years.
Infection with enterohemorrhagic Escherichia coli (EHEC) was confirmed in 79% of cases. Five years after diagnosis, 70% of EHEC-infected patients (95% confidence interval [CI], .63-.76) were fully recovered. The remaining 30% had persistent hypertension (9%), neurological symptoms (4%), decreased glomerular filtration rate (7%), and/or proteinuria (18%). Hypertension and proteinuria developed in a total of 18% of patients who had no sequelae 1 year after the acute phase (95% CI, 12-26). Multivariate logistic regression analysis demonstrated an association between the use of plasma therapy during acute phase and poor long-term outcome (odds ratio, 2.9-13; 95% CI, 2.4-33; P < .05), but this treatment was also used more frequently in severe cases. In contrast, the use of antibiotic therapy in the diarrheal phase and other established risk factors for developing HUS, such as Shiga toxin 2 and EHEC serotypes traditionally considered to be "high risk," were not associated with adverse long-term outcome. In particular, there was no difference between O157 and non-O157 EHEC.
This study identified an association between the use of plasma treatment and poor long-term outcome and confirms already known risk factors for poor prognosis. Follow-up investigations for at least 5 years are recommended to detect late-emerging sequelae.
[Show abstract][Hide abstract] ABSTRACT: Vitamin D supplementation for the prevention of rickets is one of the oldest and most effective prophylactic measures in medicine, having virtually eradicated rickets in North America. Given the potentially toxic effects of vitamin D, the recommendations for the optimal dose are still debated, in part owing to the increased incidence of idiopathic infantile hypercalcemia in Britain in the 1950s during a period of high vitamin D supplementation in fortified milk products. We investigated the molecular basis of idiopathic infantile hypercalcemia, which is characterized by severe hypercalcemia, failure to thrive, vomiting, dehydration, and nephrocalcinosis.
We used a candidate-gene approach in a cohort of familial cases of typical idiopathic infantile hypercalcemia with suspected autosomal recessive inheritance. Identified mutations in the vitamin D-metabolizing enzyme CYP24A1 were evaluated with the use of a mammalian expression system.
Sequence analysis of CYP24A1, which encodes 25-hydroxyvitamin D 24-hydroxylase, the key enzyme of 1,25-dihydroxyvitamin D(3) degradation, revealed recessive mutations in six affected children. In addition, CYP24A1 mutations were identified in a second cohort of infants in whom severe hypercalcemia had developed after bolus prophylaxis with vitamin D. Functional characterization revealed a complete loss of function in all CYP24A1 mutations.
The presence of CYP24A1 mutations explains the increased sensitivity to vitamin D in patients with idiopathic infantile hypercalcemia and is a genetic risk factor for the development of symptomatic hypercalcemia that may be triggered by vitamin D prophylaxis in otherwise apparently healthy infants.
New England Journal of Medicine 06/2011; 365(5):410-21. DOI:10.1056/NEJMoa1103864 · 55.87 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Acute antibody-mediated rejections (aAMR) after renal transplantation are defined by rapidly deteriorating graft function, detection of donor-specific antibodies (DSA) and characteristic histological features. In adults, anti-rejection strategies comprise intravenous immunoglobulin (IVIG), steroid pulses, plasmapheresis and rituximab. Data of children with aAMR are scarce. We report four episodes of aAMR in three children (aged 10, 10 and 11 years respectively) occurring early after renal transplantation. Pre-transplant complement-dependent cytotoxicity crossmatches were negative; in the case of re-transplantation repeated antigens were excluded. Basic immunosuppression comprised cyclosporine A, MMF and steroids. All four rejection episodes were histologically proven and associated with acute renal failure. De novo DSAs were detected in two aAMRs; one patient was additionally tested positive for AT1-receptor antibodies. All aAMRs were treated with steroid pulses, tacrolimus, MMF, IVIG, plasmapheresis and one single dose of rituximab. Despite therapy one graft was lost; in the remaining three cases kidney function re-established within 1-8 weeks. At follow-up, 14, 15 and 22 months' post-rejection their GFRs were 65, 88 and 105 ml/min/1.73 m(2) respectively. A combined therapy of steroid pulses, IVIG, plasmapheresis and rituximab is potentially effective in the treatment of aAMR in children.
[Show abstract][Hide abstract] ABSTRACT: Mutations in podocyte genes are associated with steroid-resistant nephrotic syndrome (SRNS), mostly affecting younger age groups. To date, it is unclear whether these patients benefit from intensified immunosuppression with cyclosporine A (CsA). The aim of this study was to evaluate the influence of podocyte gene defects in congenital nephrotic syndrome (CNS) and pediatric SRNS on the efficacy of CsA therapy and preservation of renal function. Design, settings, participants, & measurements: Genotyping was performed in 91 CNS/SRNS patients, irrespective of age at manifestation or response to CsA.
Mutations were identified in 52% of families (11 NPHS1, 17 NPHS2, 11 WT1, 1 LAMB2, 3 TRPC6). Sixty-eight percent of patients with nongenetic SRNS responded to CsA, most of them achieved complete remission. In contrast, none of the patients with genetic CNS/SRNS experienced a complete remission and only two (17%) achieved a partial response, both affected by a WT1 mutation. Preservation of renal function was significantly better in children with nongenetic disease after a mean follow-up time of 8.6 years (ESRD in 29% versus 71%).
The mutation detection rate in our population was high (52%). Most patients with genetic CNS/SRNS did not benefit from CsA with significantly lower response rates compared with nongenetic patients and showed rapid progression to end-stage renal failure. These data strongly support the idea not to expose CNS/SRNS patients with inherited defects related to podocyte function to intensified immunosuppression with CsA.
Clinical Journal of the American Society of Nephrology 11/2010; 5(11):2075-84. DOI:10.2215/CJN.01190210 · 4.61 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Nephronophthisis associated ciliopathies (NPHP-AC) comprise a group of autosomal recessive cystic kidney diseases that includes nephronophthisis (NPHP), Senior-Loken syndrome (SLS), Joubert syndrome (JBTS), and Meckel-Gruber syndrome (MKS). To date, causative mutations in NPHP-AC have been described for 18 different genes, rendering mutation analysis tedious and expensive. To overcome the broad genetic locus heterogeneity, a strategy of DNA pooling with consecutive massively parallel resequencing (MPR) was devised.
In 120 patients with severe NPHP-AC phenotypes, five pools of genomic DNA with 24 patients each were prepared which were used as templates in order to PCR amplify all 376 exons of 18 NPHP-AC genes (NPHP1, INVS, NPHP3, NPHP4, IQCB1, CEP290, GLIS2, RPGRIP1L, NEK8, TMEM67, INPP5E, TMEM216, AHI1, ARL13B, CC2D2A, TTC21B, MKS1, and XPNPEP3). PCR products were then subjected to MPR on an Illumina Genome-Analyser and mutations were subsequently assigned to their respective mutation carrier via CEL I endonuclease based heteroduplex screening and confirmed by Sanger sequencing.
For proof of principle, DNA from patients with known mutations was used and detection of 22 out of 24 different alleles (92% sensitivity) was demonstrated. MPR led to the molecular diagnosis in 30/120 patients (25%) and 54 pathogenic mutations (27 novel) were identified in seven different NPHP-AC genes. Additionally, in 24 patients only single heterozygous variants of unknown significance were found.
The combined approach of DNA pooling followed by MPR strongly facilitates mutation analysis in broadly heterogeneous single gene disorders. The lack of mutations in 75% of patients in this cohort indicates further extensive heterogeneity in NPHP-AC.
Journal of Medical Genetics 11/2010; 48(2):105-16. DOI:10.1136/jmg.2010.082552 · 6.34 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: 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.
Human Mutation 09/2010; 31(9):992-1002. DOI:10.1002/humu.21304 · 5.14 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Despite an improved conservative therapy of end stage renal failure, dialysis associated complications and diet restrictions are not compatible with the normal development of a child. Renal transplantation is the primary goal in the therapy of end stage renal disease in childhood. Due to the increasing number of patients on the waiting list and the lack of organs for transplantation each transplant centre has to optimize and to extend the renal transplant program.This study evaluated the local pediatric renal transplant program in Muenster/Germany between 1981 and 2009 with special regard to the differences between kidney transplantation before and after 1995.The data were taken from the local registry documented in the Eurotransplant ENIS program.Since 1981, 138 kidney transplantations were performed in 127 children younger than 18 years (mean age: 11.6 ± 4.5 years). Since 1995 an increase was documented in the number of kidney transplantations per year (3.6 to 6.2), the number of living related (31 versus 1) and pre-emptive transplantations (7 versus 2). The mean recipient age and the time on dialysis remained stable. Before 1995 the transplant survival after 1 and 5 years was 80.3% and 60.2%, respectively. Thereafter the transplant survival improved to 96.8% (p=0.025) and 80.4% (p=0.015).In summary an increase of pediatric kidney transplantations was documented. Living related and pre-emptive renal transplantation has been established without decreasing the time on dialysis. The 1 and 5 year transplant survival have clearly improved.
[Show abstract][Hide abstract] ABSTRACT: 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
[Show abstract][Hide abstract] ABSTRACT: Autosomal recessive polycystic kidney disease (ARPKD) [MIM 263200] belongs to a group of congenital hepatorenal fibrocystic syndromes and is caused by mutations in the PKHD1 gene encoding the multidomain protein fibrocystin/polyductin (FPC). The serine-threonine kinase mammalian target of rapamycin (mTOR) is one of the most important gate-keepers integrating numerous signals related to cell proliferation and growth. Whereas the direct activation of mTOR has been shown recently in autosomal-dominant PKD, no data are available on the role of mTOR signalling in proliferation and progression of ARPKD.
Formalin-fixed and paraffin-embedded kidney specimens obtained during nephrectomy from children with ARPKD (n = 12) were used for immunohistochemical investigation of FPC expression (monoclonal antibody (mAb) 18, mAb 5a), proliferative activity (Ki-67) and activation of the mTOR pathway. Kidney specimens from children (n = 4) who died from causes not associated with kidney disease served as controls. For the detection of AKT, mTOR and S6K antibodies specifically recognizing the activated (phosphorylated) isoforms of these proteins were used. In all patients mutation analysis of the PKHD1 gene was performed.
In 10 out of 12 patients, we could confirm the diagnosis by the identification of PKHD1 mutations. The tubular cyst epithelium of all kidney specimens stained strongly positive with the FPC-specific monoclonal antibody (mAb) 18 but only very faint signals were obtained with mAb 5a. In contrast, healthy kidneys showed rather weak signals with both FPC-specific mAbs, indicating dysregulated expression of FPC in our patients. Phosphorylated AKT as well as activated mTOR and its down-stream effector S6K were strongly expressed in cystic epithelia of all kidney specimens but not in control tissues. No association between the activation of this pathway and the proliferative activity (Ki-67 expression) was observed.
Our results point to a central role of AKT/mTOR signalling in ARPKD and justify further investigations to evaluate the therapeutic potential of mTOR inhibitors in ARPKD patients.
[Show abstract][Hide abstract] ABSTRACT: Familial hypomagnesemia with hypercalciuria and nephrocalcinosis (FHHNC) is a rare autosomal recessive tubular disorder caused by CLDN16 mutations. CLDN16 encodes the renal tight junction protein claudin-16, which is important for the paracellular reabsorption of calcium and magnesium in the thick ascending limb of Henle's loop. That FHHNC is frequently associated with progressive renal failure suggests additional roles for claudin-16 in the maintenance of tight junction integrity. An investigation of 32 patients with FHHNC and 17 different mutations was previously reported; here, the analysis is expanded to 39 additional patients and 12 new mutations. Expression studies revealed that five of the 12 new mutations led to partial loss of claudin-16 function and the remaining seven led to complete loss of function. The 23 patients who had mutations resulting in complete loss of function of both alleles were significantly younger at the onset of symptoms than the 46 patients who had at least one mutant allele providing partial function (2.2 versus 5.6 years; P < 0.01). In addition, those with complete loss of function had a more rapid decline in GFR (7.3 versus 2.9 ml/min per 1.72 m2/y; P < 0.01), leading to 54% requiring renal replacement therapy by age 15 compared with 20% of those with residual function (P < 0.05). These data suggest that residual function of claudin-16 may delay the progression of renal failure in FHHNC.
Journal of the American Society of Nephrology 02/2008; 19(1):171-81. DOI:10.1681/ASN.2007060709 · 9.34 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Acute focal bacterial nephritis (AFBN), formerly known as lobar nephronia, is a rare form of interstitial bacterial nephritis. Most often described in adults with diabetes, there is only limited knowledge of AFBN in children. Ultrasound shows circular hypoechogenic, hypoperfused parenchyma lesions, which may be misdiagnosed as a renal abscess or tumor. From 1984 to 2005, AFBN was diagnosed in 30 children at the University Hospital Münster and the General Hospital Celle, Germany. Data of 25 cases (14 girls, 11 boys) were available for retrospective evaluation. Twenty-five children with AFBN, mean age 4.5 years (range: 0.25-17.5 years), were followed up on average 4.2 years (range: 0.5-11 years). All children were admitted to hospital due to fever and rapid deterioration of clinical condition, initially suspected of having meningitis (four patients), urinary tract infections (five patients), renal tumor (three patients), pneumonia (two patients), appendicitis (one patient), or with only unspecific symptoms (ten patients). AFBN was diagnosed by ultrasound on average 3 days (range: 1-10 days) after onset of symptoms. Pyuria was found in 18/25 children, bacteriuria in 20/25 children, and hematuria in one patient. Blood cultures were negative in all but one patient. Urinary tract abnormalities were found in 12 children, including vesicoureteral reflux (8), megaureter (1), urethral valves (1), unilateral renal hypoplasia (1), and one patient with megacystis, megaureter, caudal dystopic left kidney combined with hypoplasia and dysplasia of the right kidney. High-resolution ultrasound showed AFBN lesions to have resolved completely within 12 weeks after onset of intravenous antibiotic therapy in 20/25 children. Renal parenchymal cysts remained in three cases and focal scarring in two. Blood pressure and renal function was normal in 24/25 cases. AFBN should be suspected in children with fever and rapid deterioration of clinical condition. Residual lesions such as cysts or scarring of renal parenchyma could remain.