Immunoglobulin-Negative DNAJB9-Associated Fibrillary Glomerulonephritis: A Report of 9 Cases.

Fibrillary glomerulonephritis (FGN) was previously defined by glomerular deposition of haphazardly oriented fibrils that stain with antisera to immunoglobulins but do not stain with Congo red. We report what is to our knowledge the first series of immunoglobulin-negative FGN, consisting of 9 adults (7 women and 2 men) with a mean age at diagnosis of 66 years. Patients presented with proteinuria (100%; mean protein excretion, 3g/d), hematuria (100%), and elevated serum creatinine level (100%). Comorbid conditions included carcinoma in 3 and hepatitis C virus infection in 2; no patient had hypocomplementemia or monoclonal gammopathy. Histologically, glomeruli were positive for DNAJB9, showed mostly mild mesangial hypercellularity and/or sclerosis, and were negative for immunoglobulins by immunofluorescence on frozen and paraffin tissue. Ultrastructurally, randomly oriented fibrils measuring 13 to 20nm in diameter were seen intermingling with mesangial matrix in all and infiltrating glomerular basement membranes in 5. On follow-up (mean duration, 21 months), 2 had disease remission, 4 had persistently elevated serum creatinine levels and proteinuria, and 3 required kidney replacement therapy. Thus, rare cases of FGN are not associated with glomerular immunoglobulin deposition, and the diagnosis of FGN in these cases can be confirmed by DNAJB9 immunostaining. Pathogenesis remains to be elucidated.

Prognosis and acute complications at the first onset of idiopathic nephrotic syndrome in children: a nationwide survey in Japan (JP-SHINE study).

BACKGROUND: Information on the epidemiology of idiopathic nephrotic syndrome (INS) in children, complications of INS and the side effects of steroid therapy is scarce. METHODS: The Japanese Pediatric Survey Holding Information of Nephrotic Syndrome, a nationwide cohort study, was conducted by the Japanese Study Group of Renal Disease in Children and enrolled 2099 children with newly diagnosed INS between 1 January 2010 and 31 December 2012. We conducted a follow-up study of the complications during the first onset and the patients' prognosis in this cohort. RESULTS: We obtained follow-up data on 999 children (672 males) with a median age at onset of 4.5 years [interquartile range (IQR) 2.8-9.4] and a median follow-up period of 4.1 years (IQR 2.5-5.1). At the first onset, 24% of patients experienced severe acute kidney injury (AKI), defined as a serum creatinine increase to a level two or more times the baseline. On logistic regression analysis, age, hematuria, severe hypoalbuminemia (serum albumin <1.0 g/dL) and severe bacterial infection were not independent factors, but female sex {hazard ratio [HR] 1.5 [95% confidence interval (CI) 1.1-1.7]} and hypertension [HR 4.0 (95% CI 2.6-6.0)] were significantly related to AKI. During the observation period, ocular hypertension requiring treatment occurred in 17.4% of patients, among which 0.4% received surgical treatment. Progression to frequently relapsing nephrotic syndrome/steroid-dependent nephrotic syndrome in 3 years was seen in 44.2% of the patients and was shown by the Cox regression analysis to be significantly related to younger age and days until remission at the first episode, but not to sex, hematuria, the minimum serum albumin level or AKI. Two patients died during the observation period. One patient showed progression to end-stage kidney disease. CONCLUSION: Based on the results of a multicenter questionnaire survey, the overall survival and renal survival rates were found to be excellent. However, proper management of complications, particularly in AKI and ocular hypertension, is mandatory.

A case report of a young girl with recurrent hematuria: a missed diagnosis - renal nutcracker syndrome.

BACKGROUND: Nutcracker syndrome is an easily missed cause of hematuria in children. It is characterized by left renal vein entrapment between the abdominal aorta and the superior mesenteric artery causing renal venous hypertension. Intermittent hematuria and orthostatic proteinuria with or without abdominal or flank pain are the common clinical manifestations. Presence of variable non-specific symptoms and non-significant physical findings results in a delayed diagnosis. CASE PRESENTATION: We present a ten -year -old girl with four episodes of painless gross hematuria and recurrent microscopic hematuria since the age of two years. Doppler ultrasound showed left renal vein compression while 3 D computerized tomography angiography confirmed the diagnosis of an anterior nutcracker. The patient was conservatively treated with nutritional support (pediasure complete formula and high calorie food), iron supplements and followed up, monitored for anemia, hypertension and renal insufficiency. CONCLUSION: Nutcracker syndrome is a rare cause of recurrent gross hematuria in children. A high index of suspicion and proper imaging is needed to reach a proper diagnosis and avoid the psychological and financial stress on the family.

Activated natural killer T cells in mice induce acute kidney injury with hematuria through possibly common mechanisms shared by human CD56+ T cells.

Although activation of mouse natural killer T (NKT) cells by α-galactosylceramide (α-GalCer) causes failure of multiple organs, including the kidneys, the precise mechanisms underlying kidney injury remain unclear. Here, we showed that α-GalCer-activated mouse NKT cells injured both kidney vascular endothelial cells and tubular epithelial cells in vitro, causing acute kidney injury (AKI) with hematuria in middle-aged mice. The perforin-mediated pathway was mainly involved in glomerular endothelial cell injury, whereas the TNF-α/Fas ligand pathway played an important role in the injury of tubular epithelial cells. Kidney injury in young mice was mild but could be significantly exacerbated if NKT cells were strongly activated by NK cell depletion alone or in combination with IL-12 pretreatment. When stimulated by a combination of IL-2 and IL-12, human CD56+ T cells, a functional counterpart of mouse NKT cells, also damaged both glomerular endothelial cells and tubular epithelial cells, with the former being affected in a perforin-dependent manner. These data suggest that both mouse NKT cells and human CD56+ T cells are integral to the processes that mediate AKI. Targeting CD56+ T cells may, therefore, be a promising approach to treat AKI.

Three Novel Heterozygous COL4A4 Mutations Result in Three Different Collagen Type IV Kidney Disease Phenotypes.

Thin basement membrane nephropathy (TBMN), autosomal dominant Alport syndrome (ADAS), and focal segmental glomerulosclerosis (FSGS) are kidney diseases that differ in clinical diagnosis, treatment, and prognosis. Nevertheless, they may result from the same causative genes. Here, we report 3 COL4A4 heterozygous mutations (p.Gly208Arg, p.Ser513Glufs*2, and p.Met1617Cysfs*39) that lead to 3 different collagen type IV kidney disease phenotypes, manifesting as TBMN, ADAS, and FSGS. Using bioinformatics analyses and pedigree verification, we show that these novel variants are pathogenetic and cosegregate with TBMN, ADAS, and FSGS. Furthermore, we found that the collagen type IV-associated kidney disease phenotypes are heterogeneous, with overlapping pathology and genetic mutations. We propose that COL4A4-associated TBMN, ADAS, and FSGS should be considered as collagen type IV kidney disease subtypes that represent different phases of disease progression.

Neuropilin1 regulates glomerular function and basement membrane composition through pericytes in the mouse kidney.

Neuropilin1 (Nrp1) is a co-receptor best known to regulate the development of endothelial cells and is a target of anticancer therapies. However, its role in other vascular cells including pericytes is emergent. The kidney is an organ with high pericyte density and cancer patients develop severe proteinuria following administration of NRP1B-neutralizing antibody combined with bevacizumab. Therefore, we investigated whether Nrp1 regulates glomerular capillary integrity after completion of renal development using two mouse models; tamoxifen-inducible NG2Cre to delete Nrp1 specifically in pericytes and administration of Nrp1-neutralizing antibodies. Specific Nrp1 deletion in pericytes did not affect pericyte number but mutant mice developed hematuria with glomerular basement membrane defects. Despite foot process effacement, albuminuria was absent and expression of podocyte proteins remained unchanged upon Nrp1 deletion. Additionally, these mice displayed dilation of the afferent arteriole and glomerular capillaries leading to glomerular hyperfiltration. Nidogen-1 mRNA was downregulated and collagen4α3 mRNA was upregulated with no significant effect on the expression of other basement membrane genes in the mutant mice. These features were phenocopied by treating wild-type mice with Nrp1-neutralizing antibodies. Thus, our results reveal a postdevelopmental role of Nrp1 in renal pericytes as an important regulator of glomerular basement membrane integrity. Furthermore, our study offers novel mechanistic insights into renal side effects of Nrp1 targeting cancer therapies.

Metabolic risk factors in children with asymptomatic hematuria.

BACKGROUND: Idiopathic or benign hematuria is diagnosed in children after all other possible causes have been ruled out and test results for renal or urologic pathologies are negative. METHODS: To identify possible urinary risk factors for hematuria in children, we retrospectively evaluated clinical onset, family history, and metabolic risk factors of 60 children with idiopathic hematuria but without renal stones or other pathologic conditions that could explain the hematuria. All patients followed the same ambulatory protocol at that used to evaluate kidney stone-formers. RESULTS: Seven patients had microhematuria, three patients each had microhematuria and gross hematuria, and the remaining 50 patients had gross hematuria onset. A family history of stone disease was found in 63 % of the children. At least one urinary metabolic abnormality was present in 49 patients, while 11 patients had no metabolic abnormality. The most common urinary risk factor was idiopathic hypercalciuria (single or associated), which was found in 43.5 % of patients, followed by hypocitraturia (single or associated), present in 31.7 %. Unduly acidic urine pH as a single abnormality was found in 10 % of this pediatric patient population. We also found hyperoxaluria and, less frequently, hypomagnesuria, and hyperuricosuria. CONCLUSIONS: Asymptomatic idiopathic hematuria in pediatric patients may often be associated to different urinary biochemical abnormalities, similar to what is observed in pediatric kidney stone-formers.

Collagen type IV-related nephropathies in Portugal: pathogenic COL4A3 and COL4A4 mutations and clinical characterization of 25 families.

Pathogenic mutations in genes COL4A3/COL4A4 are responsible for autosomal Alport syndrome (AS) and thin basement membrane nephropathy (TBMN). We used Sanger sequencing to analyze all exons and splice site regions of COL4A3/COL4A4, in 40 unrelated Portuguese probands with clinical suspicion of AS/TBMN. To assess genotype-phenotype correlations, we compared clinically relevant phenotypes/outcomes between homozygous/compound heterozygous and apparently heterozygous patients. Seventeen novel and four reportedly pathogenic COL4A3/COL4A4 mutations were identified in 62.5% (25/40) of the probands. Regardless of the mutated gene, all patients with ARAS manifested chronic renal failure (CRF) and hearing loss, whereas a minority of the apparently heterozygous patients had CRF or extrarenal symptoms. CRF was diagnosed at a significantly younger age in patients with ARAS. In our families, the occurrence of COL4A3/COL4A4 mutations was higher, while the prevalence of XLAS was lower than expected. Overall, a pathogenic COL4A3/COL4A4/COL4A5 mutation was identified in >50% of patients with fewer than three of the standard diagnostic criteria of AS. With such a population background, simultaneous next-generation sequencing of all three genes may be recommended as the most expedite approach to diagnose collagen IV-related glomerular basement membrane nephropathies.

Protective effects of lipoic acid and mesna on cyclophosphamide-induced haemorrhagic cystitis in mice.

The protective roles of lipoic acid (LA)/vitamin C (VC) and mesna on preventing cyclophosphamide (CYP)-induced haemorrhagic cystitis (HC) were investigated. Swiss mice were divided into five groups randomly. HC was induced by a single dose of CYP injection (150-mg kg(-1) bodyweight). Group I was injected with saline (four times in total) throughout as control group. Group II received CYP and three equal doses of saline. Group III received CYP and three doses of mesna, whereas Group IV (or Group V) received CYP, mesna + two doses of VC (or LA). All injections were performed intraperitoneally. After 24 h of cystitis induction, the bladders were collected for all the experiments. Histological characterization showed that CYP injection resulted in severe HC. Reactive oxygen species (ROS) and thiobarbituric acid reactive substances' levels were increased in CYP group. The activities of antioxidant enzymes, e.g. superoxide dismutase, catalase, glutathione S-transferase and glutathione peroxidase, were inhibited significantly in CYP groups, respectively. In addition, activation of c-jun N-terminal kinases (JNK) and p38 mitogen-activated protein kinase (MAPK) may be involved in the mechanism of CYP-induced HC but not extracellular signal regulated kinases (ERK). Significant suppression of p38 phosphorylation on Group V suggests that LA and mesna may have synergistic beneficial effect. In Groups III-V, all the parameters of HC and oxidative stress were inhibited significantly. Taking together, we found that these results illustrated that ROS play an important role on CYP-induced HC and the administration of LA/VC with mesna may have therapeutic potential against CYP-induced bladder HC.

Unusual presentations of BK virus infections in pediatric renal transplant recipients.

BKV has emerged as a significant pathogen in the field of transplantation, predominantly causing BKV nephropathy in renal transplant recipients and hemorrhagic cystitis in HSCT recipients. However, case reports describe more diverse complications, and we too present three unusual cases of BKV infections in pediatric renal transplant recipients. First, we describe a case of biopsy-proven renal damage secondary to BKV prior to the onset of viremia, demonstrating that BKV nephropathy can occur without preceding viremia. We also present two renal transplant recipients with persistent BK viruria, one with BKV-associated hemorrhagic cystitis and the other with microscopic hematuria. Therefore, we conclude that BKV manifestations may be more diverse than previously thought and suggest clinical utility in urine BKV qPCR testing in specific transplant recipients.

Tonsillar TLR9 expression and efficacy of tonsillectomy with steroid pulse therapy in IgA nephropathy patients.

BACKGROUND: Patients with IgA nephropathy (IgAN) often show aggravation of renal injury with macroscopic hematuria after mucosal infections, especially tonsillitis. We previously demonstrated the important role of mucosal Toll-like receptor 9 (TLR9) activation in the pathogenesis of murine IgAN. Moreover, a single nucleotide polymorphism (SNP) in TLR9 was significantly associated with pathological severity in human IgAN. In this study, we investigated correlations between tonsillar TLR9 messenger RNA expression, TLR9 SNP genotypes and clinical outcomes following tonsillectomy with steroid pulse therapy (SPT) in IgAN patients. METHODS: Tonsillar TLR9 expression was examined in IgAN (n = 49) and control (n = 15) patients who had undergone tonsillectomy. The correlations between tonsillar TLR9 expression level, TLR9 SNP genotypes and clinical outcomes after tonsillectomy with SPT were examined. RESULTS: High expression of tonsillar TLR9 was observed in ∼23% of IgAN patients. These patients showed stronger and earlier remission of hematuria and proteinuria than those with low TLR9 expression. Patients with the TT genotype of TLR9 SNP (rs352140) had more severe renal damage than those with other genotypes. Patients whose serum IgA level decreased more than average after tonsillectomy (large ΔIgA) showed higher cumulative remission rates of proteinuria than patients with a smaller decrease in these levels (small ΔIgA). CT/CC genotypes were more dominant and tonsillar TLR9 expressions significantly higher in large ΔIgA patients than in small ΔIgA patients. CONCLUSION: In IgAN patients, expression levels of tonsillar TLR9 and TLR9 SNP were well correlated with the efficacy of tonsillectomy with SPT.

Periostin Attenuates Cyclophosphamide-induced Bladder Injury by Promoting Urothelial Stem Cell Proliferation and Macrophage Polarization.

Interstitial cystitis (IC) is a bladder syndrome of unclear etiology with no generally accepted treatment. Growing evidence suggest that periostin (POSTN) is an important homeostatic component in the tissue repair and regeneration in adulthood, but its function in urinary bladder regeneration is still unknown. Here we investigate whether POSTN is involved in bladder tissue repair in a cyclophosphamide (CYP)-induced interstitial cystitis model. POSTN is primarily expressed in bladder stroma (detrusor smooth muscle and lamina propria) and upregulated in response to CYP-induced injury. POSTN deficiency resulted in more severe hematuria, aggravated edema of the bladder, and delayed umbrella cell recovery. Besides, less proliferative urothelial cells (labeled by pHH3, Ki67, and EdU) and lower expression of Krt14 (a urothelial stem cell marker) were detected in POSTN-/- mice post CYP exposure, indicating a limited urothelial regeneration. Further investigations revealed that POSTN could induce Wnt4 upregulation and activate AKT signaling, which together activates ß-catenin signaling to drive urothelial stem cell proliferation. In addition, POSTN can promote resident macrophage proliferation and polarization to a pro-regenerative (M2) phenotype, which favors urothelial regeneration. Furthermore, we generated injectable P-GelMA granular hydrogel as a biomaterial carrier to deliver recombinant POSTN into the bladder, which could increase urothelial stem cells number, decrease umbrella cells exfoliation, and hence alleviate hematuria in a CYP-induced interstitial cystitis model. In summary, our findings identify a pivotal role of POSTN in bladder urothelial regeneration and suggest that intravesical biomaterials-assisted POSTN delivery may be an efficacious treatment for interstitial cystitis.

Heterogeneous stock rats: a new model to study the genetics of renal phenotypes.

Chronic kidney disease is a growing medical concern, with an estimated 25.6 million people in the United States exhibiting some degree of kidney injury and/or decline in kidney function. Animal models provide great insight into the study of the genetics of complex diseases. In particular, heterogeneous stock (HS) rats represent a unique genetic resource enabling rapid fine-mapping of complex traits. However, they have not been explored as a model to study renal phenotypes. To evaluate the usefulness of HS rats in the genetics of renal traits, a time course evaluation (weeks 8-40) was performed for several renal phenotypes. As expected, a large degree of variation was seen for most renal traits. By week 24, three (of 40) rats exhibited marked proteinuria that increased gradually until week 40 and ranged from 33.7 to 80.2 mg/24 h. Detailed histological analysis confirmed renal damage in these rats. In addition, several rats consistently exhibited significant hematuria (5/41). Interestingly, these rats were not the same rats that exhibited proteinuria, indicating that susceptibility to different types of kidney injury is likely segregating within the HS population. One HS rat exhibited unilateral renal agenesis (URA), which was accompanied by a significant degree of proteinuria and glomerular and tubulointerstitial injury. The parents of this HS rat were identified and bred further. Additional offspring of this pair were observed to exhibit URA at frequency between 40% and 60%. In summary, these novel data demonstrate that HS rats exhibit variation in proteinuria and other kidney-related traits, confirming that the model harbors susceptibility alleles for kidney injury and providing the basis for further genetic studies.

Toll-like receptor 4 expression is increased in circulating mononuclear cells of patients with immunoglobulin A nephropathy.

We investigated Toll-like receptors (TLR-3, -4 and -7) expression in circulating mononuclear cells of patients with immunoglobulin A nephropathy (IgAN), a disease with debated relationships with mucosal immunity. TLR-4 expression (detected by fluorescence activated cell sorter) and mRNA transcriptional levels (Taqman) were significantly higher in patients with IgAN than in healthy controls (P = 0.00200 and P = 0.0200). TLR-3 and TLR-7 were not modified significantly. In IgAN patients proteinuria was correlated significantly with TLR-4 expression (P = 0.0312). In a group of nephrotic syndromes, TLR-3, -4 and -7 expression was similar to healthy controls. A significant difference in TLR-4 expression and mRNA levels was found between very active IgAN patients (proteinuria > 1 g/1.73 m(2)/day in association with severe microscopic haematuria) and inactive patients (proteinuria < 0.5 g/1.73 m(2)/day, with absent or minimal haematuria). No correlation with levels of aberrantly glycosylated IgA1, age, renal biopsy features or therapy was found. This study shows for the first time an up-regulation of TLR-4 in circulating mononuclear cells of patients with IgAN, particularly in association with proteinuria and heavy microscopic haematuria.

C1q nephropathy in a child presenting with recurrent gross hematuria.

C1q nephropathy is a rare glomerular disease characterized by mesangial immune deposits with dominant or codominant staining for C1q. The exact pathogenesis leading to the mesangial immune deposits of C1q remains unknown. C1q nephropathy often presents with proteinuria in the nephrotic range, with an unpredictable or poor response to corticosteroid therapy. It is seen more commonly in older children and young adults and is more common in African Americans compared with Caucasians. We present a 4-year-old African American girl who presented with recurrent gross hematuria in the absence of proteinuria or hypertension and whose renal biopsy demonstrated dominant mesangial deposits of C1q. We conclude that C1q nephropathy should be considered in patients who present with recurrent gross hematuria.

A longitudinal study of urinary dipstick parameters in wild chimpanzees (Pan troglodytes verus) in Côte d'Ivoire.

We performed 796 dip-stick tests on urine from 100 wild West African chimpanzees (Pan troglodytes verus) from 4 habituated groups in the tropical rain forest of Taï National Park, Cote d'Ivoire, to establish reference values for health monitoring. Specific gravity was also measured on 359 urine samples from 62 chimpanzees. The effect of age, sex, group, month, estrus, pregnancy, meat consumption, and acute respiratory disease on pH, leucocytes, protein, blood, hemoglobin, and glucose was examined using ordinal logistic regression. The presence of nitrite, ketones, bilirubin, and urobilinogen in urine was also recorded. Outbreak of acute respiratory disease did not influence any of the urinary parameters. Thirty-seven percent of the samples had a pH <7 and the whole range of pH was found through the year, in all age groups, and in both sexes. Meat consumption lowered the urinary pH. Our results show that all pH levels must be considered normal for the West African chimpanzee subspecies P. troglodytes verus living in the rainforest. We also found a cluster of glucose-positive samples at a specific point in time which was not attributed to diabetes mellitus. These findings highlight that there are differences in normal physiological parameters among wild chimpanzees living in different habitats.

The prevalence of Th17 cells and FOXP3 regulate T cells (Treg) in children with primary nephrotic syndrome.

The aim of this study was to investigate the prevalence of interleukin (IL)-17-producing CD4+ T cells (Th17) and regulatory T (Treg) cells in children with primary nephrotic syndrome. The study cohort consisted of 62 children who were randomly divided into control, primary nephrotic syndrome, and isolated hematuria groups. Flow cytometric analysis revealed the presence of Th17 cells in the peripheral blood mononuclear cells (PBMCs) of 35 children and Tregs in the PBMCs of all children. In addition, mRNA expression of Th17-related factors [IL-17, -23p19 and retinoid orphan nuclear receptor (RORc)] and the concentration of plasma inflammatory mediators such as IL-6 and IL-1beta were consistently detected in all children. Protein expression of IL-17 and transforming growth factor-beta1 were also detected in renal biopsy tissue and compared between different groups. Patients with PNS were found to have an increased number of Th17 cells and decreased numbers of Tregs in their PBMCs, and there was significant difference in the prevalence of Th17 and Tregs between the patients with PNS and those with isolated hematuria. Our data show that among our study cohort, there was a dynamic equilibrium between Th17 and Treg cells in children with PNS following the development of PNS with apparent renal tubular epithelial cell and interstitium lesions. The dynamic interaction between Th17 and Treg cells may be important in the development of PNS.

Urinary metabolic abnormalities in children with idiopathic hematuria.

BACKGROUND: Hematuria, either macroscopic or microscopic, is an incidental finding of multiple nephrologic or urologic disorders. Disturbances of urine inhibitors or promotors have been suggested as the potential causes of isolated idiopathic hematuria in children and its recurrence. Meanwhile, appropriate treatment of these risk factors might improve secondary asymptomatic or macroscopic hematuria. OBJECTIVES: The aim of this study was to identify contribution of urinary biochemical abnormalities in children with isolated idiopathic hematuria. METHODS: About 522 children with isolated hematuria were evaluated in a prospective cross-sectional study. Data such as clinical manifestations, family history, laboratory examinations, structural anomalies, and urine biochemistry were obtained. Patients with nephrolithiasis, nephrocalcinosis, tubulointerstitial disorder, genitourinary abnormality, urinary tract infection, and glomerular disorder were excluded from the study. Variables such as calcium, citrate, oxalate, phosphate, uric acid, cystine, and magnesium were measured in 24-h urine collection. In addition, serum levels of electrolytes, urea, creatinine, parathyroid hormone, and bicarbonate were identified. RESULTS: Mean age at diagnosis was 5.9 years, and females outnumbered males (2/1). Of those, 88.5% had microscopic hematuria, and 12.6% experienced episodes of gross hematuria. Abdominal pain was the most common clinical manifestations. Urinary tract infection occurred in 30% of cases. Totally, 94% of patients had single or multiple metabolic abnormalities in 24-h urine excretion including hypocitraturia, 60.7%; hypomagnesuria, 58.2%; hyperuricosuria, 35.8%; hypercalciuria, 33.7%; hyperoxaluria, 33.7%; and cystinuria, 0.76%, respectively. About 8% of cases had mixed urine metabolic disturbances. Most patients had mild hematuria (red blood cell <10/high power field (hpf)), and 18% had significant hematuria (>30/hpf), with no statistical correlation to urine metabolic abnormalities. About 80% of patients had a history of nephrolithiasis in their relatives. DISCUSSION: Decreased urinary inhibitor concentration followed by increased stimulator concentration were the most common abnormalities in patients with idiopathic hematuria. Accordingly, measurement of urinary biochemical concentration is highly recommended in children with isolated hematuria. In addition, investigating the therapeutic effect of potassium citrate supplements is highly recommended in these patients to prevent future stone formation and treatment of hematuria.

COL4A3/COL4A4 mutations link familial hematuria and focal segmental glomerulosclerosis. glomerular epithelium destruction via basement membrane thinning?

The recent description of multiple gene defects in hereditary podocytopathies and in hereditary glomerular basement membrane diseases has dramatically improved the current state of our knowledge on the renal glomerular filtration barrier. Recently described mutations in collagen IV and laminin in patients with hematuria and severe nephrotic syndrome add to other experimental data supporting the hypothesis that the glomerular basement membrane (GBM) may also have a significant role in protein filtration, a function previously attributed exclusively to the podocytes. Collagen IV heterozygous mutations were thought to cause only a mild form of renal disease (thin basement membrane nephropathy--TBMN). However, data from our laboratory show that many patients who carry such mutations may later on in life develop focal and segmental glomerulosclerosis, on top of the TBMN and the microscopic hematuria, a situation that frequently progresses to chronic renal failure or even end-stage renal disease. The role of unknown modifier genes may explain the heterogeneity of symptoms in TBMN and other glomerular diseases and in particular the selected development of chronic renal failure. The molecular communication between GBM and podocytes may also be a key factor in the search for these major genetic modifiers while their understanding may improve novel drug design for glomerular diseases.