C3 Glomerulopathy and Related Disorders in Children: Etiology-Phenotype Correlation and Outcomes.

BACKGROUND AND OBJECTIVES: Membranoproliferative GN and C3 glomerulopathy are rare and overlapping disorders associated with dysregulation of the alternative complement pathway. Specific etiologic data for pediatric membranoproliferative GN/C3 glomerulopathy are lacking, and outcome data are based on retrospective studies without etiologic data. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: A total of 80 prevalent pediatric patients with membranoproliferative GN/C3 glomerulopathy underwent detailed phenotyping and long-term follow-up within the National Registry of Rare Kidney Diseases (RaDaR). Risk factors for kidney survival were determined using a Cox proportional hazards model. Kidney and transplant graft survival was determined using the Kaplan-Meier method. RESULTS: Central histology review determined 39 patients with C3 glomerulopathy, 31 with immune-complex membranoproliferative GN, and ten with immune-complex GN. Patients were aged 2-15 (median, 9; interquartile range, 7-11) years. Median complement C3 and C4 levels were 0.31 g/L and 0.14 g/L, respectively; acquired (anticomplement autoantibodies) or genetic alternative pathway abnormalities were detected in 46% and 9% of patients, respectively, across all groups, including those with immune-complex GN. Median follow-up was 5.18 (interquartile range, 2.13-8.08) years. Eleven patients (14%) progressed to kidney failure, with nine transplants performed in eight patients, two of which failed due to recurrent disease. Presence of >50% crescents on the initial biopsy specimen was the sole variable associated with kidney failure in multivariable analysis (hazard ratio, 6.2; 95% confidence interval, 1.05 to 36.6; P<0.05). Three distinct C3 glomerulopathy prognostic groups were identified according to presenting eGFR and >50% crescents on the initial biopsy specimen. CONCLUSIONS: Crescentic disease was a key risk factor associated with kidney failure in a national cohort of pediatric patients with membranoproliferative GN/C3 glomerulopathy and immune-complex GN. Presenting eGFR and crescentic disease help define prognostic groups in pediatric C3 glomerulopathy. Acquired abnormalities of the alternative pathway were commonly identified but not a risk factor for kidney failure.

Mitochondrial Haplogroup and the Risk of Acute Kidney Injury Following Cardiac Bypass Surgery.

Although mitochondrial dysfunction plays a key role in the pathophysiology of acute kidney injury (AKI), the influence of mitochondrial genetic variability in this process remains unclear. We explored the association between the risk of post-cardiac bypass AKI and mitochondrial haplotype - inherited mitochondrial genomic variations of potentially functional significance. Our single-centre study recruited consecutive patients prior to surgery. Exclusions included stage 5 CKD, non-Caucasian race and subsequent off-pump surgery. Haplogroup analysis allowed characterisation of the study population using the common mutations and by phylogenetic supergroup (WXI and HV). Chi-square tests for association allowed the identification of potential predictors of AKI for use in logistic regression analysis. AKI occurred in 12.8% of the study population (n = 881; male 69.6%, non-diabetic 78.5%, median (interquartile range) age 68.0 (61.0-75.0) years). The haplogroup profile comprised H (42.7%), J (12.1%), T (10.9%), U (14.4%) and K (7.6%). Although the regression model was statistically significant (χ2 = 95.483, p < 0.0005), neither the phylogenetic supergroups nor any individual haplogroup was a significant contributor. We found no significant association between common European haplogroups and the risk of post-cardiac bypass AKI. However, given the major role of mitochondrial dysfunction in AKI, there is a need to replicate our findings in other cohorts and with other aetiologies of AKI.

Genome-wide linkage and association study implicates the 10q26 region as a major genetic contributor to primary nonsyndromic vesicoureteric reflux.

Vesicoureteric reflux (VUR) is the commonest urological anomaly in children. Despite treatment improvements, associated renal lesions - congenital dysplasia, acquired scarring or both - are a common cause of childhood hypertension and renal failure. Primary VUR is familial, with transmission rate and sibling risk both approaching 50%, and appears highly genetically heterogeneous. It is often associated with other developmental anomalies of the urinary tract, emphasising its etiology as a disorder of urogenital tract development. We conducted a genome-wide linkage and association study in three European populations to search for loci predisposing to VUR. Family-based association analysis of 1098 parent-affected-child trios and case/control association analysis of 1147 cases and 3789 controls did not reveal any compelling associations, but parametric linkage analysis of 460 families (1062 affected individuals) under a dominant model identified a single region, on 10q26, that showed strong linkage (HLOD = 4.90; ZLRLOD = 4.39) to VUR. The ~9Mb region contains 69 genes, including some good biological candidates. Resequencing this region in selected individuals did not clearly implicate any gene but FOXI2, FANK1 and GLRX3 remain candidates for further investigation. This, the largest genetic study of VUR to date, highlights the 10q26 region as a major genetic contributor to VUR in European populations.

Use of eculizumab in crescentic IgA nephropathy: proof of principle and conundrum?

IgA nephropathy (IgAN) is characterized by a variable clinical course and multifaceted pathophysiology. There is substantial evidence to suggest that complement activation plays a pivotal role in the pathogenesis of the disease. Therefore, complement inhibition using the humanized anti-C5 monoclonal antibody eculizumab could be a rational treatment. We report here a 16-year-old male with the vasculitic form of IgAN who failed to respond to aggressive conventional therapy including high-dose steroids, cyclophosphamide and plasma exchange and who was treated with four weekly doses of 900 mg eculizumab followed by a single dose of 1200 mg. He responded rapidly to this treatment and has had a stable creatinine around 150 µmol/L (1.67 mg/dL) for >6 months. However, proteinuria was unabated on maximal conventional anti-proteinuric treatment, and a repeat renal biopsy 11 months after presentation revealed severe chronic changes. We believe this case provides proof of principle that complement inhibition may be beneficial in IgAN but also that development of chronicity may be independent of complement.

Prevalence in the General Population of a CFH Sequence Variant Associated with Atypical Haemolytic Uraemic Syndrome in an Extensive Family from Southwest England.

BACKGROUND/AIMS: Twenty-five members of a family from the county of Devon in England have been affected by atypical haemolytic uraemic syndrome (aHUS) associated with a CFH mutation (c.3643C>G; p.Arg1215Gly). A 65-year-old male was diagnosed with aHUS after losing a renal transplant to a thrombotic microangiopathy. Subsequent mutation screening revealed the same CFH mutation without him being knowingly related to the local kindred. We designed a study to investigate the prevalence of this mutation in the local area. In addition, we examined the diagnoses of pre-existing haemodialysis patients to determine whether other patients might unknowingly be at risk of carrying the same CFH mutation. METHODS: The Exeter Ten Thousand (EXTEND) study aims to recruit 10,000 healthy volunteers over the age of 18 years living within 25 miles of Exeter in Devon. We genotyped DNA from 4,000 EXTEND subjects for CFH c.3643C>G; p.Arg1215Gly. We reviewed the diagnoses of 294 haemodialysis patients in the Devon area and genotyped 7 patients with either end-stage renal disease of unknown aetiology, malignant hypertension or renovascular disease. RESULTS: CFH c.3643C>G; p.Arg1215Gly was not detected in any of the 7 haemodialysis patients or the 4,000 individuals within the EXTEND study. CONCLUSIONS: We conclude that CFH c.3643C>G; p.Arg1215Gly is not endemic in Devon. This reinforces our existing practice of genotyping only patients with kidney disease and evidence of a thrombotic microangiopathy for this mutation. This is the first study looking at the prevalence of CFH mutations in the general population.

Primary, nonsyndromic vesicoureteric reflux and nephropathy in sibling pairs: a United Kingdom cohort for a DNA bank.

BACKGROUND AND OBJECTIVES: Primary vesicoureteric reflux (VUR) can coexist with reflux nephropathy (RN) and impaired renal function. VUR appears to be an inherited condition and is reported in approximately one third of siblings of index cases. The objective was to establish a DNA collection and clinical database from U.K. families containing affected sibling pairs for future VUR genetics studies. The cohort's clinical characteristics have been described. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: Most patients were identified from tertiary pediatric nephrology centers; each family had an index case with cystography-proven primary, nonsyndromic VUR. Affected siblings had radiologically proven VUR and/or radiographically proven RN. RESULTS: One hundred eighty-nine index cases identified families with an additional 218 affected siblings. More than 90% were <20 years at the study's end. Blood was collected and leukocyte DNA extracted from all 407 patients and from 189 mothers and 183 fathers. Clinical presentation was established in 122; 92 had urinary tract infections and 16 had abnormal antenatal renal scans. RN was radiologically proven in 223 patients. Four patients had been transplanted; none were on dialysis. In 174 others aged >1 year, estimated GFR (eGFR) was calculated. Five had eGFR 15 to 59 and 48 had eGFR 60 to 89 ml/min per 1.73 m(2). Values were lower in bilateral RN patients than in those with either unilateral or absent RN. CONCLUSIONS: The large DNA collection from families with VUR and associated RN constitutes a resource for researchers exploring the most likely complex, genetic components predisposing to VUR and RN.

Whole-genome linkage and association scan in primary, nonsyndromic vesicoureteric reflux.

Primary vesicoureteric reflux accounts for approximately 10% of kidney failure requiring dialysis or transplantation, and sibling studies suggest a large genetic component. Here, we report a whole-genome linkage and association scan in primary, nonsyndromic vesicoureteric reflux and reflux nephropathy. We used linkage and family-based association approaches to analyze 320 white families (661 affected individuals, generally from families with two affected siblings) from two populations (United Kingdom and Slovenian). We found modest evidence of linkage but no clear overlap with previous studies. We tested for but did not detect association with six candidate genes (AGTR2, HNF1B, PAX2, RET, ROBO2, and UPK3A). Family-based analysis detected associations with one single-nucleotide polymorphism (SNP) in the UK families, with three SNPs in the Slovenian families, and with three SNPs in the combined families. A case-control analysis detected associations with three additional SNPs. The results of this study, which is the largest to date investigating the genetics of reflux, suggest that major loci may not exist for this common renal tract malformation within European populations.

Is complement factor H a susceptibility factor for IgA nephropathy?

There is substantial evidence to suggest that complement activation plays a pivotal role in the pathogenesis of IgA nephropathy. Mesangial C3 deposition is seen in approximately 90% of patients and polymeric IgA has been shown to activate the alternative and lectin pathways. In addition there have been reports of deficiency and mutations in the serum complement regulator factor H (CFH) in association with IgA nephropathy. In this study we have examined the hypothesis that CFH is a susceptibility factor for IgA nephropathy. In 46 IgA nephropathy patients we undertook genotyping of three CFH SNPS (rs3753394, rs3753396 and rs1065489). There was no significant difference in the allele frequency of these 3 SNPs between the patients and normal controls. In the same group of patients we undertook mutation screening of CFH exons 18-23 using direct sequencing and found no abnormalities. All the patients had a normal serum factor H concentration. In this small cohort of IgA nephropathy patients we have not found evidence to support the hypothesis that factor H is a major susceptibility factor for the disease.

Nutritional screening in patients on hemodialysis: is subjective global assessment an appropriate tool?

OBJECTIVE: Malnutrition is common in patients with chronic renal failure and should be screened for systematically. Subjective global assessment (SGA) is frequently used, but it is time-consuming. The aim of this study was to assess the sensitivity of SGA as a screening tool for malnutrition compared with the measurement of body mass index (BMI) and serum albumin combined with a history of unintentional weight loss. DESIGN: This was a cross-sectional study. SETTING: The study was undertaken in two hospital hemodialysis units. PATIENTS AND INTERVENTION: A total of 141 patients on hemodialysis were studied. Nutritional assessment was undertaken with a seven-point SGA, measurement of height, weight and serum albumin, and a record of unintentional weight loss. OUTCOMES: Patients were considered to be at risk of malnutrition if any of the following three criteria were met: a serum albumin less than 35 g/L, a BMI less than 18.5, and unintentional weight loss of edema free weight greater than 10% in the past 6 months. A diagnosis of malnutrition was made if the SGA score was between 1 and 5. RESULTS: A total of 41 patients had either a serum albumin less than 35 g/L or a BMI less than 18.5 or unintentional weight loss of edema free weight of more than 10% in the past 6 months. Of these 41 patients, 29 had a serum albumin less than 35 g/L, 9 had a BMI less than 18.5, and 15 had unintentional loss of edema free weight greater than 10% in the past 6 months. Thirteen patients were judged by SGA to be mild to moderately malnourished. All 13 were identified by serum albumin, BMI, or weight loss. CONCLUSIONS: In this study, measurement of SGA did not diagnose malnutrition in any patients in whom this had not already been potentially identified by measurement of serum albumin, BMI, and a history of weight loss. SGA did not therefore increase the sensitivity of nutritional screening in this cohort.

Atypical relapse of hemolytic uremic syndrome after transplantation.

Atypical hemolytic uremic syndrome (HUS) frequently leads to end-stage renal failure and can relapse after transplantation. A 12-year-old girl presenting with familial atypical HUS with a factor H mutation was successfully transplanted 6 years after a first transplant that had failed because of immediate recurrent HUS. Prophylactic plasma exchange before and after transplantation was used. Two months after transplantation, concomitant with a reduction in plasma exchange frequency, the plasma creatinine increased from 70 micro mol/l to 194 micro mol/l in 2 weeks without thrombocytopenia or signs of hemolytic anemia. The patient had minimal clinical symptoms and a presumptive diagnosis of graft rejection was made. Despite treatment with six daily pulses of methylprednisolone, plasma creatinine continued to increase and a graft biopsy was therefore undertaken. This showed the typical appearance of a thrombotic microangiopathy without any evidence of rejection. Despite daily plasmapheresis and replacement of cyclosporine with tacrolimus, there was no improvement and transplant nephrectomy was undertaken. This patient demonstrates that HUS can recur in a kidney transplant without the diagnostic hematological features and emphasizes the need for early transplant biopsy in such patients showing a decline in transplant function.

Solitary functioning kidney and diverse genital tract malformations associated with hepatocyte nuclear factor-1beta mutations.

BACKGROUND: Renal tract malformations are, on occasion, associated with uterine malformations. The transcription factor hepatocyte nuclear factor (HNF)-1beta is expressed from the earliest stages of development of the Wolffian duct, the mesonephros and metanephros, and the Müllerian ducts in the mouse. In adult mice HNF-1beta is expressed in the kidney tubules, collecting ducts, and in the oviducts and uterus in the female (Müllerian duct derivatives) and in the epididymis, vas deferens and seminal vesicles (Wolffian duct derivatives) in the male. HNF-1beta mutations have been reported in two families where affected members have renal abnormalities, female genital tract malformations and early-onset diabetes. Renal and uterine abnormalities have not been described in families without early-onset diabetes. METHODS: We sequenced the HNF-1beta gene in nine subjects with renal abnormalities and a personal or family history of female genital tract malformations, but no history of diabetes. RESULTS: Two families were identified with novel HNF-1beta mutations: a missense mutation in exon 2 with conversion of serine to proline at codon 151 (S151P) and a frameshift mutation in exon 3 with a 1 base pair deletion at codon 243 (Q243fsdelC). The S151P mutation proband has cystic kidneys and uterus didelphys. Her affected second son has renal cysts and hypospadias. The Q243fsdelC proband has a single functioning kidney and her two children have renal dysplasia. Histology in one child shows cystic dysplasia with a lack of glomeruli. The proband's sister is a mutation carrier and has a bicornuate uterus. Diabetes is not a feature in either family. CONCLUSIONS: This study confirms an association between HNF-1beta mutations and renal and Müllerian anomalies. The hypospadias may be coincidental. This study describes the first HNF-1beta mutations that are associated with a single functioning kidney and the absence of diabetes. This study further reinforces the variability of the renal and non-renal phenotypes associated with HNF-1beta mutations.

Skeletal muscle mRNA levels for cathepsin B, but not components of the ubiquitin-proteasome pathway, are increased in patients with lung cancer referred for thoracotomy.

Muscle wasting is a common and prominent feature of advanced cancer, including lung cancer. Evidence from animal experiments suggests that accelerated proteolysis via the ubiquitin--proteasome pathway is the primary cause of cancer-related cachexia. However, there are few data on the role of this pathway in determining muscle wasting in human cancer. The present study was designed to measure whether skeletal muscle gene expression of components of the ubiquitin-proteasome pathway and/or the lysosomal proteolytic pathway was increased in patients with early lung cancer. A total of 36 patients with lung cancer referred for curative resection and 10 control subjects had biopsies of latissimus dorsi muscle taken at operation. mRNA levels of four components of the ubiquitin-proteasome pathway, i.e. polyubiquitin, C2 alpha proteasome subunit, 14 kDa ubiquitin-carrier protein and ubiquitin-activating protein, and of two lysosomal proteolytic enzymes, i.e. cathepsin B and cathepsin D, were measured using quantitative Northern blotting. mRNA levels for cathepsin B, but not for components of the ubiquitin--proteasome pathway, were higher in patients with cancer compared with controls (P=0.01). Among lung cancer patients, cathepsin B mRNA levels correlated with fat-free mass index (r = -0.57, P=0.003) and tumour stage (r(s)=0.45, P=0.03), and were higher in smokers (P=0.04). Thus gene expression of the lysosomal protease cathepsin B is increased in the skeletal muscle of patients with early lung cancer, and the strong inverse relationship with fat-free mass suggests that cathepsin B may have a role in inducing muscle wasting in the early stages of lung cancer.