Association of problems, coping styles, and preferred online activity with depression, anxiety, and other psychological disorders in Turkish adolescents diagnosed with chronic kidney disease.

BACKGROUND: To assess depression, anxiety, and other psychological disorders in adolescents with chronic kidney disease (CKD) and determine the significant factors and the effect of digital media use on its scores among these patient groups. METHODS: The study was conducted as a cross-sectional study and included 84 adolescents with CKD and 68 healthy controls. The participants completed the Revised Child Anxiety and Depression Scale (RCADS). We recorded their age, gender, the most problematic issue in their lives, coping methods with problems, and online applications they prefer in their leisure time. RESULTS: Elevated rates (scores > 70) of separation anxiety, panic disorder, obsession, depression, total anxiety, and total depression scales were statistically higher in the CKD group. Separation anxiety, panic disorder, obsession, total anxiety, and total depression scales were higher in girls, and panic disorder, obsession, depression, total anxiety, and total depression scores were higher in younger ages in multivariate analysis. In the CKD group, family issues/problems increased panic disorder, obsession, depression, total anxiety, and total depression scales. Crying in tears/yelling response in children while facing a problem was associated with increased separation anxiety and social phobia rates. Also, preferring video applications was associated with separation anxiety and messaging applications with depression, total anxiety, and total depression. CONCLUSIONS: Adolescents with CKD are at risk for depression, anxiety, obsession, and panic disorders. Also, crying in tears/yelling response may be at greater risk for anxiety among CKD adolescents. Early psychiatric evaluation and routine psychiatric follow-ups initiated early may improve the mental health of this vulnerable population.

Magnetic resonance imaging based kidney volume assessment for risk stratification in pediatric autosomal dominant polycystic kidney disease.

Introduction: In the pediatric context, most children with autosomal dominant polycystic kidney disease (ADPKD) maintain a normal glomerular filtration rate (GFR) despite underlying structural kidney damage, highlighting the critical need for early intervention and predictive markers. Due to the inverse relationship between kidney volume and kidney function, risk assessments have been presented on the basis of kidney volume. The aim of this study was to use magnetic resonance imaging (MRI)-based kidney volume assessment for risk stratification in pediatric ADPKD and to investigate clinical and genetic differences among risk groups. Methods: This multicenter, cross-sectional, and case-control study included 75 genetically confirmed pediatric ADPKD patients (5-18 years) and 27 controls. Kidney function was assessed by eGFR calculated from serum creatinine and cystatin C using the CKiD-U25 equation. Blood pressure was assessed by both office and 24-hour ambulatory measurements. Kidney volume was calculated from MRI using the stereological method. Total kidney volume was adjusted for the height (htTKV). Patients were stratified from A to E classes according to the Leuven Imaging Classification (LIC) using MRI-derived htTKV. Results: Median (Q1-Q3) age of the patients was 6.0 (2.0-10.0) years, 56% were male. There were no differences in sex, age, height-SDS, or GFR between the patient and control groups. Of the patients, 89% had PKD1 and 11% had PKD2 mutations. Non-missense mutations were 73% in PKD1 and 75% in PKD2. Twenty patients (27%) had hypertension based on ABPM. Median htTKV of the patients was significantly higher than controls (141 vs. 117 ml/m, p = 0.0003). LIC stratification revealed Classes A (38.7%), B (28%), C (24%), and D + E (9.3%). All children in class D + E and 94% in class C had PKD1 variants. Class D + E patients had significantly higher blood pressure values and hypertension compared to other classes (p > 0.05 for all). Discussion: This study distinguishes itself by using MRI-based measurements of kidney volume to stratify pediatric ADPKD patients into specific risk groups. It is important to note that PKD1 mutation and elevated blood pressure were higher in the high-risk groups stratified by age and kidney volume. Our results need to be confirmed in further studies.

Humoral and cellular immune response to SARS-CoV-2 mRNA BNT162b2 vaccine in pediatric kidney transplant recipients compared with dialysis patients and healthy children.

BACKGROUND: Compared with the general population, the immune response to COVID-19 mRNA vaccines is lower in adult kidney transplant recipients (KTRs). However, data is limited for pediatric KTRs. In this study, we aimed to assess humoral and cellular immune responses to the COVID-19 mRNA vaccine in pediatric KTRs. METHODS: This multicenter, prospective, case-control study included 63 KTRs (37 male, aged 12-21 years), 19 dialysis patients, and 19 controls. Humoral (anti-SARS-CoV2 IgG, neutralizing Ab (nAb)) and cellular (interferon-gamma release assay (IGRA)) immune responses were assessed at least one month after two doses of BNT162b2 mRNA vaccine. RESULTS: Among COVID-19 naïve KTRs (n = 46), 76.1% tested positive for anti-SARS-CoV-2 IgG, 54.3% for nAb, and 63% for IGRA. Serum levels of anti-SARS-CoV-2 IgG and nAb activity were significantly lower in KTRs compared to dialysis and control groups (p < 0.05 for all). Seropositivity in KTRs was independently associated with shorter transplant duration (p = 0.005), and higher eGFR (p = 0.007). IGRA titer was significantly lower than dialysis patients (p = 0.009). Twenty (43.4%) KTRs were positive for all immune parameters. Only four of 11 seronegative KTRs were IGRA-positive. COVID-19 recovered KTRs had significantly higher anti-SARS-CoV-2 IgG and nAb activity levels than COVID-19 naïve KTRs (p = 0.018 and p = 0.007, respectively). CONCLUSIONS: The humoral and cellular immune responses to SARS-CoV-2 mRNA BNT162b2 vaccine are lower in pediatric KTRs compared to dialysis patients. Further prospective studies are required to demonstrate the clinical efficacy of the mRNA vaccine in KTRs. This prospective study was registered in ClinicalTrials.gov (NCT05465863, registered retrospectively at 20.07.2022). A higher resolution version of the Graphical abstract is available as Supplementary information.

Urinary HSP70 improves diagnostic accuracy for urinary tract infection in children: UTILISE study.

BACKGROUND: The accuracy of conventional urinalysis in diagnosing urinary tract infection (UTI) in children is limited, leading to unnecessary antibiotic exposure in a large fraction of patients. Urinary heat shock protein 70 (uHSP70) is a novel marker of acute urinary tract inflammation. We explored the added value of uHSP70 in discriminating UTI from other infections and conditions confused with UTI. METHODS: A total of 802 children from 37 pediatric centers in seven countries participated in the study. Patients diagnosed with UTI (n = 191), non-UTI infections (n = 178), contaminated urine samples (n = 50), asymptomatic bacteriuria (n = 26), and healthy controls (n = 75) were enrolled. Urine and serum levels of HSP70 were measured at presentation in all patients and after resolution of the infection in patients with confirmed UTI. RESULTS: Urinary (u)HSP70 was selectively elevated in children with UTI as compared to all other conditions (p < 0.0001). uHSP70 predicted UTI with 89% sensitivity and 82% specificity (AUC = 0.934). Among the 265 patients with suspected UTI, the uHSP70 > 48 ng/mL criterion identified the 172 children with subsequently confirmed UTI with 90% sensitivity and 82% specificity (AUC = 0.862), exceeding the individual diagnostic accuracy of leukocyturia, nitrite, and leukocyte esterase positivity. uHSP70 had completely normalized by the end of antibiotic therapy in the UTI patients. Serum HSP70 was not predictive. CONCLUSIONS: Urine HSP70 is a novel non-invasive marker of UTI that improves the diagnostic accuracy of conventional urinalysis. We estimate that rapid urine HSP70 screening could spare empiric antibiotic administration in up to 80% of children with suspected UTI. A higher resolution version of the Graphical abstract is available as Supplementary information.

A broad clinical spectrum of PLCε1-related kidney disease and intrafamilial variability.

BACKGROUND: The phenotypic and genotypic spectrum and kidney outcome of PLCε1-related kidney disease are not well known. We attempted to study 25 genetically confirmed cases of PLCε1-related kidney disease from 11 centers to expand the clinical spectrum and to determine the relationship between phenotypic and genotypic features, kidney outcome, and the impact of treatment on outcome. METHODS: Data regarding demographics, clinical and laboratory characteristics, histopathological and genetic test results, and treatments were evaluated retrospectively. RESULTS: Of 25 patients, 36% presented with isolated proteinuria, 28% with nephrotic syndrome, and 36% with chronic kidney disease stage 5. Twenty patients underwent kidney biopsy, 13 (65%) showed focal segmental glomerulosclerosis (FSGS), and 7 (35%) showed diffuse mesangial sclerosis (DMS). Of the mutations identified, 80% had non-missense, and 20% had missense; ten were novel. No clear genotype-phenotype correlation was observed; however, significant intrafamilial variations were observed in three families. Patients with isolated proteinuria had significantly better kidney survival than patients with nephrotic syndrome at onset (p = 0.0004). Patients with FSGS had significantly better kidney survival than patients with DMS (p = 0.007). Patients who presented with nephrotic syndrome did not respond to any immunosuppressive therapy; however, 4/9 children who presented with isolated proteinuria showed a decrease in proteinuria with steroids and/or calcineurin inhibitors. CONCLUSION: PLCε1-related kidney disease may occur in a wide clinical spectrum, and genetic variations are not associated with clinical presentation or disease course. However, clinical presentation and histopathology appear to be important determinants for prognosis. Immunosuppressive medications in addition to angiotensin-converting enzyme inhibitors may be beneficial for selected patients. "A higher resolution version of the Graphical abstract is available as Supplementary information".

COVID-19 in pediatric patients undergoing chronic dialysis and kidney transplantation.

The study aims to present the incidence of COVID-19 in pediatric patients undergoing renal replacement therapy (RRT) and to compare the severity and outcomes of the disease between the dialysis and kidney transplant (KTx) groups. This multicenter observational study was conducted between 1 April and 31 December 2020 in Istanbul. Members of the Istanbul branch of the Turkish Pediatric Nephrology Association were asked to report all confirmed cases of COVID-19 who were on RRT, as well as the number of prevalent RRT patients under the age of 20. A total of 46 confirmed cases of COVID-19 were reported from 12 centers, of which 17 were dialysis patients, and 29 were KTx recipients. Thus, the incidence rate of COVID-19 was 9.3% among dialysis patients and 9.2% among KTx recipients over a 9-month period in Istanbul. Twelve KTx recipients and three dialysis patients were asymptomatic (p = 0.12). Most of the symptomatic patients in both the dialysis and KTx groups had a mild respiratory illness. Only two patients, one in each group, experienced a severe disease course, and only one hemodialysis patient had a critical illness that required mechanical ventilation. In the entire cohort, one hemodialysis patient with multiple comorbidities died.Conclusion: While most cases are asymptomatic or have a mild disease course, pediatric patients undergoing dialysis and a kidney transplant are at increased risk for COVID-19. What is Known: • In adult population, both dialysis patients and kidney transplant recipients are at increased risk for severe illness of COVID-19 and have higher mortality rate. • Children with kidney transplantation are not at increased risk for COVID-19 and most have mild disease course. • Data on children on dialysis are scarce. What is New: • Pediatric patients undergoing dialysis and kidney transplantation have an increased risk for COVID-19. • Most patients undergoing renal replacement therapy either on dialysis or transplanted develop asymptomatic or mild COVID-19 disease with a favorable outcome.

PROGRESS STUDY: Progression of chronic kidney disease in children and heat shock proteins.

Various molecular and cellular processes are involved in renal fibrosis, such as oxidative stress, inflammation, endothelial cell injury, and apoptosis. Heat shock proteins (HSPs) are implicated in the progression of chronic kidney disease (CKD). Our aim was to evaluate changes in urine and serum HSP levels over time and their relationships with the clinical parameters of CKD in children. In total, 117 children with CKD and 56 healthy children were examined. The CKD group was followed up prospectively for 24 months. Serum and urine HSP27, HSP40, HSP47, HSP60, HSP70, HSP72, and HSP90 levels and serum anti-HSP60 and anti-HSP70 levels were measured by ELISA at baseline, 12 months, and 24 months. The urine levels of all HSPs and the serum levels of HSP40, HSP47, HSP60, HSP70, anti-HSP60, and anti-HSP70 were higher at baseline in the CKD group than in the control group. Over the months, serum HSP47 and HSP60 levels steadily decreased, whereas HSP90 and anti-HSP60 levels steadily increased. Urine HSP levels were elevated in children with CKD; however, with the exception of HSP90, they decreased over time. In conclusion, our study demonstrates that CKD progression is a complicated process that involves HSPs, but they do not predict CKD progression. The protective role of HSPs against CKD may weaken over time, and HSP90 may have a detrimental effect on the disease course.

Primary coenzyme Q10 Deficiency-6 (COQ10D6): Two siblings with variable expressivity of the renal phenotype.

Primary coenzyme Q10 deficiency-6 (COQ10D6) is a rare autosomal recessive disorder caused by COQ6 mutations. The main clinical manifestations are infantile progressive nephrotic syndrome (NS) leading to end-stage renal disease and sensorineural deafness. A 7-year-old girl was diagnosed with steroid-resistant NS (SRNS) and an audiological work-up revealed bilateral sensorineural deafness. A renal biopsy demonstrated focal segmental glomerulosclerosis. Despite immunosuppressive therapy, her serum levels of creatinine increased and haemodialysis was indicated within 1 year after the diagnosis. Living-donor kidney transplantation was performed in the eighth month of haemodialysis. A diagnostic custom-designed panel-gene test including 30 genes for NS revealed homozygous c.1058C > A [rs397514479] in exon nine of COQ6. Her older brother, who had sensorineural hearing loss with no renal or neurological involvement, had the same mutation in homozygous form. COQ6 mutations should be considered not only in patients with SRNS with sensorineural hearing loss but also in patients with isolated sensorineural hearing loss with a family history of NS. The reported p.His174 variant of COQ8B was suggested to be a risk factor for secondary CoQ deficiency, while p.Arg174 appeared to improve the condition in a yeast model. Family segregation and the co-occurrence of biallelic p.Arg174 of COQ8B in a brother with hearing loss implied that the interaction of the altered COQ8B with the mutant COQ6 alleviated the symptoms in this family. CoQ10 replacement therapy should be initiated for these patients, as primary CoQ10 deficiency is considered the only known treatable mitochondrial disease.

Risk factors for febrile urinary tract infections in the first year after pediatric renal transplantation.

Urinary tract infection is the most common infectious complication following kidney transplant. Anatomic abnormalities, bladder dysfunction, a positive history of febrile urinary tract infection, and recipient age are reported risk factors. The aim of this study was to determine the risk factors for fUTI, which necessitated hospitalization in the first year after renal transplantation in our pediatric transplant population. A retrospective review of 195 pediatric patients who underwent kidney transplant between 2008 and 2017 from a single institution was performed. All patients admitted to the hospital with fUTI were marked for further analyses. The risk factors including age, gender, dialysis type, history of urologic disorders, and preoperative proteinuria for fUTI in the first year after kidney transplantation and graft survivals were investigated. Independent-sample t test and chi-square tests were used for univariate analysis. Exhaustive CHAID algorithm was used for multivariate analysis. The data of 115 male and 80 female patients were retracted. The mean ages of our cohort for males and females were 9.5 ± 5.1 and 10 ± 4.8 years, respectively. The age of the patients at transplant and their gender were found to be a statistically significant risk factors for developing fUTIs. Multivariate analysis showed that fUTI was common in female patients and a subgroup of male patients who had preoperative proteinuria, but no neurogenic bladder had higher risk compared with male patients without proteinuria. Patient surveillance and antibiotic prophylaxis algorithms can be developed to prevent febrile urinary tract infections seen after pediatric kidney transplantation in risky population.

Urine Levels of Matrix Metalloproteinases and Tissue Inhibitor of Metalloproteinases in Children with Type 1 Diabetes Mellitus

Objective: Histopathological changes in the kidney in type 1 diabetes mellitus (T1DM) begin before detection of microalbuminuria. Therefore, there is interest in finding a better biomarker for the early detection of diabetic kidney injury. The aim of this present study was to determine whether urinary indicators of fibrosis are detectable early in the development of T1DM in children and if they may predict progressive renal injury. Methods: Urinary matrix metalloproteinase 2 and 9 (MMP2 and MMP9), tissue inhibitor of metalloproteinase 1 and 2 (TIMP1 and TIMP2) and transforming growth factor-ß1 (TGF-ß1) were assessed in 33 patients with T1DM with normal renal functions and in 24 healthy controls. Microalbuminuria was not present in the patient group with the exception of three patients. The results were adjusted to urine creatinine (Cr) and the differences between patients and controls were evaluated. These measurements were repeated after one year and the results were compared with the first year results. Results: Urine MMP2/Cr, MMP9/Cr, TIMP1/Cr, TIMP2/Cr, TGF-ß1/Cr were not different between the patient and control groups (p>0.05). There were also no significant differences between the first and second year results for these biomarkers (p>0.05). None of these parameters were correlated with hemoglobin A1c, body mass index and duration of T1DM. Interestingly, all parameters were negatively correlated to age of onset of T1DM (p<0.05). Conclusion: Our findings suggest that urinary biomarkers of fibrosis do not show an increase in diabetic children without microalbuminuria. The results also indicate that the risk of early fibrosis may increase as age of onset of T1DM decreases.

Advillin acts upstream of phospholipase C ϵ1 in steroid-resistant nephrotic syndrome.

Steroid-resistant nephrotic syndrome (SRNS) is a frequent cause of chronic kidney disease. Here, we identified recessive mutations in the gene encoding the actin-binding protein advillin (AVIL) in 3 unrelated families with SRNS. While all AVIL mutations resulted in a marked loss of its actin-bundling ability, truncation of AVIL also disrupted colocalization with F-actin, thereby leading to impaired actin binding and severing. Additionally, AVIL colocalized and interacted with the phospholipase enzyme PLCE1 and with the ARP2/3 actin-modulating complex. Knockdown of AVIL in human podocytes reduced actin stress fibers at the cell periphery, prevented recruitment of PLCE1 to the ARP3-rich lamellipodia, blocked EGF-induced generation of diacylglycerol (DAG) by PLCE1, and attenuated the podocyte migration rate (PMR). These effects were reversed by overexpression of WT AVIL but not by overexpression of any of the 3 patient-derived AVIL mutants. The PMR was increased by overexpression of WT Avil or PLCE1, or by EGF stimulation; however, this increased PMR was ameliorated by inhibition of the ARP2/3 complex, indicating that ARP-dependent lamellipodia formation occurs downstream of AVIL and PLCE1 function. Together, these results delineate a comprehensive pathogenic axis of SRNS that integrates loss of AVIL function with alterations in the action of PLCE1, an established SRNS protein.

Neutrophil Gelatinase-Associated Lipocalin as an Early Sign of Diabetic Kidney Injury in Children.

OBJECTIVE: There is some evidence indicating that histopathological changes in type 1 diabetes mellitus (T1DM) emerge before onset of microalbuminuria. The aim of our study was to determine whether urine neutrophil gelatinase-associated lipocalin (NGAL) levels can be considered as an early sign of diabetic kidney injury. METHODS: Urine NGAL (uNGAL) levels and urinary NGAL/creatinine ratio (uNGAL/Cr) were assessed in 76 patients with T1DM and compared with the findings of 35 healthy individuals. The relationship of uNGAL levels with diabetes duration, body mass index (BMI), serum lipids, HbA1c, and microalbuminuria was also evaluated. RESULTS: Mean uNGAL (100.16±108.28 ng/mL) and uNGAL/Cr (118.93-117.97 ng/mg) levels in both microalbuminuric and non-microalbuminuric diabetic patients were found to be higher than those in the control group (uNGAL: 21.46±18.59 ng/mL and uNGAL/Cr: 32.1±51.48 ng/mg) (p=0.0001). CONCLUSION: Urine NGAL level increases in the very early phase of T1DM before microalbuminuria develops. The patients with T1DM should be considered to have diabetic kidney injury from the time of diagnosis on and preventive interventions need to be initiated at an early stage to preclude the progression to end-stage renal disease.

Whole-exome resequencing distinguishes cystic kidney diseases from phenocopies in renal ciliopathies.

Rare single-gene disorders cause chronic disease. However, half of the 6000 recessive single gene causes of disease are still unknown. Because recessive disease genes can illuminate, at least in part, disease pathomechanism, their identification offers direct opportunities for improved clinical management and potentially treatment. Rare diseases comprise the majority of chronic kidney disease (CKD) in children but are notoriously difficult to diagnose. Whole-exome resequencing facilitates identification of recessive disease genes. However, its utility is impeded by the large number of genetic variants detected. We here overcome this limitation by combining homozygosity mapping with whole-exome resequencing in 10 sib pairs with a nephronophthisis-related ciliopathy, which represents the most frequent genetic cause of CKD in the first three decades of life. In 7 of 10 sibships with a histologic or ultrasonographic diagnosis of nephronophthisis-related ciliopathy, we detect the causative gene. In six sibships, we identify mutations of known nephronophthisis-related ciliopathy genes, while in two additional sibships we found mutations in the known CKD-causing genes SLC4A1 and AGXT as phenocopies of nephronophthisis-related ciliopathy. Thus, whole-exome resequencing establishes an efficient, noninvasive approach towards early detection and causation-based diagnosis of rare kidney diseases. This approach can be extended to other rare recessive disorders, thereby providing accurate diagnosis and facilitating the study of disease mechanisms.

Exome capture reveals ZNF423 and CEP164 mutations, linking renal ciliopathies to DNA damage response signaling.

Nephronophthisis-related ciliopathies (NPHP-RC) are degenerative recessive diseases that affect kidney, retina, and brain. Genetic defects in NPHP gene products that localize to cilia and centrosomes defined them as "ciliopathies." However, disease mechanisms remain poorly understood. Here, we identify by whole-exome resequencing, mutations of MRE11, ZNF423, and CEP164 as causing NPHP-RC. All three genes function within the DNA damage response (DDR) pathway. We demonstrate that, upon induced DNA damage, the NPHP-RC proteins ZNF423, CEP164, and NPHP10 colocalize to nuclear foci positive for TIP60, known to activate ATM at sites of DNA damage. We show that knockdown of CEP164 or ZNF423 causes sensitivity to DNA damaging agents and that cep164 knockdown in zebrafish results in dysregulated DDR and an NPHP-RC phenotype. Our findings link degenerative diseases of the kidney and retina, disorders of increasing prevalence, to mechanisms of DDR.

Pseudodominant inheritance of nephronophthisis caused by a homozygous NPHP1 deletion.

Nephronophthisis (NPHP) is an autosomal recessive kidney disease characterized by tubular basement membrane disruption, interstitial infiltration, and tubular cysts. NPHP leads to end-stage renal failure (ESRD) in the first three decades of life and is the most frequent genetic cause of chronic renal failure in children and young adults. Extrarenal manifestations are known, such as retinitis pigmentosa, brainstem and cerebellar anomalies, liver fibrosis, and ocular motor apraxia type Cogan. We report on a Turkish family with clinical signs of nephronophthisis. The phenotype occurred in two generations and therefore seemed to be inherited in an autosomal dominant pattern. Nevertheless, a deletion analysis of the NPHP1 gene on chromosome 2 was performed and showed a homozygous deletion. Analysis of the family pedigree indicated no obvious consanguinity in the last three generations. However, haplotype analysis demonstrated homozygosity on chromosome 2 indicating a common ancestor to the parents of all affected individuals. NPHP1 deletion analysis should always be considered in patients with apparently dominant nephronophthisis. Furthermore, three out of four patients developed ESRD between 27 and 43 years of age, which may be influenced by yet unknown modifier genes.

Genetic diagnosis by whole exome capture and massively parallel DNA sequencing.

Protein coding genes constitute only approximately 1% of the human genome but harbor 85% of the mutations with large effects on disease-related traits. Therefore, efficient strategies for selectively sequencing complete coding regions (i.e., "whole exome") have the potential to contribute to the understanding of rare and common human diseases. Here we report a method for whole-exome sequencing coupling Roche/NimbleGen whole exome arrays to the Illumina DNA sequencing platform. We demonstrate the ability to capture approximately 95% of the targeted coding sequences with high sensitivity and specificity for detection of homozygous and heterozygous variants. We illustrate the utility of this approach by making an unanticipated genetic diagnosis of congenital chloride diarrhea in a patient referred with a suspected diagnosis of Bartter syndrome, a renal salt-wasting disease. The molecular diagnosis was based on the finding of a homozygous missense D652N mutation at a position in SLC26A3 (the known congenital chloride diarrhea locus) that is virtually completely conserved in orthologues and paralogues from invertebrates to humans, and clinical follow-up confirmed the diagnosis. To our knowledge, whole-exome (or genome) sequencing has not previously been used to make a genetic diagnosis. Five additional patients suspected to have Bartter syndrome but who did not have mutations in known genes for this disease had homozygous deleterious mutations in SLC26A3. These results demonstrate the clinical utility of whole-exome sequencing and have implications for disease gene discovery and clinical diagnosis.

Metabolic disturbances following the use of inadequate solutions for hemofiltration in acute renal failure.

Continuous renal replacement therapy (CRRT) has become an important supportive therapy for critically ill children with acute renal failure. In Turkey, commercially available diafiltration and replacement fluids cannot be found on the market. Instead, peritoneal dialysis fluids for dialysis and normal saline as replacement fluid are used. The first objective of this study was to examine metabolic complications due to CRRT treatments. The second objective was to determine demographic characteristics and outcomes of patients who receive CRRT. We did a retrospective chart review of all pediatric patients treated with CRRT between February and December 2004. Thirteen patients received CRRT; seven survived (53.8%). All patients were treated with continuous venovenous hemodiafiltration. Median patient age was 71.8 +/- 78.8 (1.5-180) months. Hyperglycemia occurred in 76.9% (n=10), and metabolic acidosis occurred in 53.8% (n=7) of patients. Median age was younger (48.8 vs.106.2 months), median urea level (106.2 vs. 71 mg/dl) and percent fluid overload (FO) (17.2% vs. 7.6%, respectively) were higher, and CRRT initiation time was longer (8.6 vs 5.6 days) in nonsurvivors vs. survivors for all patients, although these were not statistically significant. CRRT was stopped in all survivors, and four nonsurvivors (67%) were on renal replacement therapy at the time of death. Hyperglycemia and metabolic acidosis were frequently seen in CRRT patients when commercially available diafiltration fluids were not available. Using peritoneal dialysis fluid as dialysate is not a preferable solution. Early initiation of CRRT offered survival benefits to critically ill pediatric patients. Mortality was associated with the primary disease diagnosis.

The gene mutated in juvenile nephronophthisis type 4 encodes a novel protein that interacts with nephrocystin.

Nephronophthisis, the most common genetic cause of chronic renal failure in children, is a progressive tubulo-interstitial kidney disorder that is inherited as an autosomal recessive trait. The disease is characterized by polyuria, growth retardation and deterioration of renal function during childhood or adolescence. The most prominent histological features are modifications of the tubules with thickening of the basement membrane, interstitial fibrosis and, in the advanced stages, medullary cysts. Nephronophthisis can also be associated with conditions affecting extrarenal organs, such as retinitis pigmentosa (Senior-Løken syndrome) and ocular motor apraxia (Cogan syndrome). Three loci are associated with the juvenile, infantile and adolescent forms, on chromosomes 2q13 (NPHP1; refs 5,6), 9q22 (NPHP2; ref. 7) and 3q21 (NPHP3; ref. 8), respectively. NPHP1, the only gene identified so far, encodes nephrocystin, which contains a Src homology 3 (SH3) domain and interacts with intracytoplasmic proteins involved in cell adhesion. Recently, a second locus associated with the juvenile form of the disease, NPHP4, was mapped to chromosome 1p36 (ref. 14). We carried out haplotype analysis of families affected with nephronophthisis that were not linked to the NPHP1, NPHP2 or NPHP3 loci, using markers covering this region. This allowed us to reduce the NPHP4 interval to a one centimorgan interval between D1S2795 and D1S2870, which contains six genes. We identified five different mutations in one of these genes, designated NPHP4, in unrelated individuals with nephronophthisis. The NPHP4 gene encodes a 1,250-amino acid protein of unknown function that we named nephrocystin-4. We demonstrated the interaction of nephrocystin-4 with nephrocystin suggesting that these two proteins participate in a common signaling pathway.