Diagnostic Utility of Exome Sequencing Among Israeli Children With Kidney Failure.

Introduction: Genetic etiologies are estimated to account for a large portion of chronic kidney diseases (CKD) in children. However, data are lacking regarding the true prevalence of monogenic etiologies stemming from an unselected population screen of children with advanced CKD. Methods: We conducted a national multicenter prospective study of all Israeli pediatric dialysis units to provide comprehensive "real-world" evidence for the genetic basis of childhood kidney failure in Israel. We performed exome sequencing and assessed the genetic diagnostic yield. Results: Between 2019 and 2022, we recruited approximately 88% (n = 79) of the children on dialysis from all 6 Israeli pediatric dialysis units. We identified genetic etiologies in 36 of 79 (45%) participants. The most common subgroup of diagnostic variants was in congenital anomalies of the kidney and urinary tract causing genes (e.g., EYA1, HNF1B, PAX2, COL4A1, and NFIA) which together explain 28% of all monogenic etiologies. This was followed by mutations in genes causing renal cystic ciliopathies (e.g., NPHP1, NPHP4, PKHD1, and BBS9), steroid-resistant nephrotic syndrome (e.g., LAGE3, NPHS1, NPHS2, LMX1B, and SMARCAL1) and tubulopathies (e.g., CTNS and AQP2). The genetic diagnostic yield was higher among Arabs compared to Jewish individuals (55% vs. 29%) and in children from consanguineous compared to nonconsanguineous families (63% vs. 29%). In 5 participants (14%) with genetic diagnoses, the molecular diagnosis did not correspond with the pre-exome diagnosis. Genetic diagnosis has a potential influence on clinical management in 27 of 36 participants (75%). Conclusion: Exome sequencing in an unbiased Israeli nationwide dialysis-treated kidney failure pediatric cohort resulted in a genetic diagnostic yield of 45% and can often affect clinical decision making.

Long-term outcomes after pre-emptive liver transplantation in primary hyperoxaluria type 1.

BACKGROUND: Primary hyperoxaluria type 1 (PH1) is an autosomal recessive disease caused by the liver defect of oxalate metabolism, which leads to kidney failure and systemic manifestations. Until recently, liver transplantation was the only definitive treatment. The timing of liver transplantation can be early, while kidney function is still normal (pre-emptive liver transplantation-PLT), or when the patient reaches stage 5 chronic kidney disease (CKD) and needs combined liver-kidney transplantation. We aimed to determine the long-term kidney outcomes of PLT in PH1 patients. METHODS: A retrospective single-center study of PH1 patients who were followed in our center between 1997 and 2017. We compared the kidney outcomes of patients who underwent PLT to those who presented with preserved kidney function and did not undergo PLT. RESULTS: Out of 36 PH1 patients, 18 patients were eligible for PLT (eGFR > 40 mL/min/1.73 m2 at the time of diagnosis). Seven patients underwent PLT (PLT group), while 11 continued conservative treatments (PLTn group). In the PLT group, the median eGFR at the time of PLT and at the end of the follow-up period (14-20 years) was 72 (range 50-89) and 104 (range 86-108) mL/min/1.73 m2, respectively, and no patient died or reached stage 5 CKD. In the PLTn group, eight patients (72.7%) reached stage 5 CKD (median time to kidney replacement therapy was 11 years), and two patients died from disease complications (18.2%). CONCLUSIONS: Pre-emptive liver transplantation preserved kidney function in patients with PH1 in our cohort. Early intervention can prevent kidney failure and systemic oxalosis in PH1. A higher resolution version of the Graphical abstract is available as Supplementary information.

A Founder Mutation in EHD1 Presents with Tubular Proteinuria and Deafness.

BACKGROUND: The endocytic reabsorption of proteins in the proximal tubule requires a complex machinery and defects can lead to tubular proteinuria. The precise mechanisms of endocytosis and processing of receptors and cargo are incompletely understood. EHD1 belongs to a family of proteins presumably involved in the scission of intracellular vesicles and in ciliogenesis. However, the relevance of EHD1 in human tissues, in particular in the kidney, was unknown. METHODS: Genetic techniques were used in patients with tubular proteinuria and deafness to identify the disease-causing gene. Diagnostic and functional studies were performed in patients and disease models to investigate the pathophysiology. RESULTS: We identified six individuals (5-33 years) with proteinuria and a high-frequency hearing deficit associated with the homozygous missense variant c.1192C>T (p.R398W) in EHD1. Proteinuria (0.7-2.1 g/d) consisted predominantly of low molecular weight proteins, reflecting impaired renal proximal tubular endocytosis of filtered proteins. Ehd1 knockout and Ehd1R398W/R398W knockin mice also showed a high-frequency hearing deficit and impaired receptor-mediated endocytosis in proximal tubules, and a zebrafish model showed impaired ability to reabsorb low molecular weight dextran. Interestingly, ciliogenesis appeared unaffected in patients and mouse models. In silico structural analysis predicted a destabilizing effect of the R398W variant and possible inference with nucleotide binding leading to impaired EHD1 oligomerization and membrane remodeling ability. CONCLUSIONS: A homozygous missense variant of EHD1 causes a previously unrecognized autosomal recessive disorder characterized by sensorineural deafness and tubular proteinuria. Recessive EHD1 variants should be considered in individuals with hearing impairment, especially if tubular proteinuria is noted.

[RASBURICASE TREATMENT FOR NEONATAL ACUTE KIDNEY INJURY - A CASE REPORT].

INTRODUCTION: Hyperuricemia can cause renal damage and acute kidney injury or be secondary to renal failure and reduced excretion. Rasburicase, a recombinant urate oxidase, is a common treatment for hyperuricemia from different etiologies. There are scarce reports on rasburicase treatment for neonatal Acute Kidney Injury (AKI) with hyperuricemia to prevent renal damage secondary to hyperuricemia. Herein we report a case of neonatal AKI with hyperuricemia that was treated with a single dose of rasburicase. Serum uric acid declined immediately after rasburicase infusion and remained in the normal range since then. In contrast to previous reports, the normalization of uric acid levels was not accompanied by recovery from AKI and serum creatinine levels remained elevated for a long period. The neonate recovered from AKI only 2 weeks post rasburicase treatment. This case report highlights the importance of uric acid levels in neonatal AKI and suggests treatment with rasburicase in cases of hyperuricemia and acute kidney injury in neonates.

Genetic counseling of high-risk isolated populations: A worldwide challenge.

BACKGROUND: Isolated populations with high rates of consanguinity and genetic disorders can be found in most parts of the world. The aim of our paper was to highlight the unique challenges faced in genetic counseling for such patients and to discuss the ways to facilitate the difficulties, with an emphasis on the crucial role of electronic medical records (EMR). CASE: We report a couple presenting with elevated maternal alpha-fetoprotein in three pregnancies, in which an erroneous diagnosis of epidermolysis bullosa was established in the past and carried along through several years. The live born proband had no evidence of skin disease; however, soon after birth she was diagnosed with congenital nephrotic syndrome. Sequencing of NPHS1 gene yielded a homozygous likely pathogenic genetic variant c.2104G > A (p.Gly702Arg). Population screening performed in the village of residence revealed a carrier frequency of 1-47. This high frequency justified including testing for the founder genetic variant in the national program for population screening. CONCLUSIONS: Our report highlights the caution, suspicion and time investment which should be practiced and addressed in genetic counseling of high-risk isolated populations. Using EMR may facilitate reaching the correct diagnosis, enable accurate genetic counseling and provide information for decision-making to the couples, as well as "save" a large community from devastating diseases.

Focal segmental glomerulosclerosis in pediatric kidney transplantation: 30 years' experience.

From 1982 to 2011, 53 kidney transplantations (KT) for pediatric focal segmental glomerulosclerosis (FSGS) were recorded in the National Israeli Kidney Transplant Registry (NIKTR): 22-primary (1◦) FSGS, 25-proved/suspected genetic-secondary (2◦) FSGS, six lost/incomplete files/other. Half (56%) of 23 patients with 2◦ FSGS were Israeli-Arabs vs 29% of 1◦ FSGS KT recipients. 1◦ FSGS recurrence occurred in 64% (14/22) of 22 KT in 17 patients aged (median) 14 years vs 1/25 of 2◦ FSGS (P<.001). Early graft days/nonfunction occurred in 9/14 (64%), 2/8 (25%) and 2/25 (4%) of recurrent 1◦ FSGS (rFSGS), nonr1◦ FSGS and 2◦ FSGS, respectively. Twelve biopsies performed in nine of these grafts at (median) 8 days (range 5-60 days) post-KT showed: ATN-5, suspected rejection-4, rFSGS-2, normal kidney-1; rFSGS was diagnosed eventually in 8/9. Dialysis need during the first month post-KT was significantly associated with FSGS recurrence: 6/14 (43%) for rFSGS vs 2/8 (25%) for non-rFSGS. Plasmapheresis (PP) achieved complete and partial rFSGS remission in 5/9 and 2/9 grafts, respectively. Three grafts were excised during the first 60 days post-KT for: nonfunction (1) and bleeding (2). Remaining grafts' GFR was: 78, 42, and 91 mL/min (median) at 5.3, 4.75, and 8 years follow-up for non-rFSGS, rFSGS, and 2◦ FSGS grafts, respectively. CONCLUSIONS: Early PP implementation should be considered after KT for 1◦ FSGS patients with early graft dysfunction despite delayed proteinuria and nonspecific biopsy.

Urinary tract infections caused by community-acquired extended-spectrum ß-lactamase-producing and nonproducing bacteria: a comparative study.

OBJECTIVE: To study the clinical characteristics and associated risk factors of urinary tract infections (UTIs) caused by community-acquired extended-spectrum ß-lactamase (CA-ESBL)-producing Enterobacteriaceae. STUDY DESIGN: A case-control study at a large community hospital in northern Israel, comparing children who had UTI due to CA-ESBL (n = 25) and CA non-ESBL (n = 125) in 2008-2011. Data were collected from medical charts, telephonic questionnaires administered to all participants, and groups were compared. RESULTS: During the study period, the yearly incidence of CA-ESBL UTI increased significantly. There were no significant differences between the CA-ESBL and CA non-ESBL groups in demographics and clinical outcome. Compared with CA non-ESBL UTI, children with CA-ESBL UTI had a longer hospital stay (5.9 ± 3.3 vs 3.9 ± 2.3 days; P = .003) and higher rates of recent hospitalization (28% vs 4%; P = .001), previous UTI (40% vs 13%; P = .003), urinary tract anomalies (32% vs 5%; P < .001), UTI prophylaxis with cephalexin (32% vs 2%; P < .005), and aminoglycoside resistance. In a multivariate analysis, UTI prophylaxis (OR 12.5 [CI 2.7-58]), recent hospitalization (OR 4.8 [CI 1.1-21]), and Klebsiella spp. UTI (OR 4.7 [CI 1.3-17]), were risk factors for CA-ESBL UTI. CONCLUSIONS: Children prescribed UTI prophylaxis (due to urinary tract anomalies or recurrent UTI) with cephalexin and those with previous hospitalizations are at increased risk for CA-ESBL UTI. Although not associated with higher rates of complications, the multidrug resistant phenotype of CA-ESBL isolates poses a challenge in choosing appropriate empiric and definitive therapy and prolongs hospital stay.

Post-transplantation lymphoproliferative disorder in pediatric kidney-transplant recipients - a national study.

PTLD is the most common malignancy in pediatric kidney-transplant recipients. We examined the prevalence, clinical features, and outcome of PTLD in Israel. Twelve (4.4%) of 272 pediatric (<19 yr) kidney-transplant recipients retrieved from a search of the NIKTR for 1991-2008 had acquired PTLD at a median of 3.2 yr post-transplantation. PTLD-affected patients were younger at transplantation (4.2 vs. 12.5 yr, p = 0.02), had a higher rate of OKT3 therapy for acute rejection (25% vs. 4%, p = 0.015), and 5/12 were EBV-seropositive at transplantation. Graft dysfunction was the presenting sign in six (50%). PTLD was predominantly abdominal (83%) and B-cell type (67%); T-cell PTLD occurred exclusively in EBV-seropositive patients. Treatment consisted of immunosuppression cessation (6/12, 50%), antiviral agents (7/12, 58%), anti-CD20 monoclonal antibodies (4/12, 33%), and chemotherapy (6/12, 50%). Survival was 100% in the EBV-naïve patients and 40% in the EBV-seropositive patients. Graft loss occurred in three of eight survivors (37.5%). PTLD-associated mortality risk was older age: 11.2 vs. 3.4 yr, longer dialysis: 15 vs. 6.5 months, T-cell type disease (75%), later PTLD onset: 6.35 vs. 1.9 yr post-transplantation and era of transplantation (43% mortality before vs. 20% after 2001). Pretransplantation EBV-seronegative status might confer a survival benefit with early detected PTLD. EBV-seropositive patients are at risk for aggressive late-onset lethal PTLD.

Mutations in DHDPSL are responsible for primary hyperoxaluria type III.

Primary hyperoxaluria (PH) is an autosomal-recessive disorder of endogenous oxalate synthesis characterized by accumulation of calcium oxalate primarily in the kidney. Deficiencies of alanine-glyoxylate aminotransferase (AGT) or glyoxylate reductase (GRHPR) are the two known causes of the disease (PH I and II, respectively). To determine the etiology of an as yet uncharacterized type of PH, we selected a cohort of 15 non-PH I/PH II patients from eight unrelated families with calcium oxalate nephrolithiasis for high-density SNP microarray analysis. We determined that mutations in an uncharacterized gene, DHDPSL, on chromosome 10 cause a third type of PH (PH III). To overcome the difficulties in data analysis attributed to a state of compound heterozygosity, we developed a strategy of "heterozygosity mapping"-a search for long heterozygous patterns unique to all patients in a given family and overlapping between families, followed by reconstruction of haplotypes. This approach enabled us to determine an allelic fragment shared by all patients of Ashkenazi Jewish descent and bearing a 3 bp deletion in DHDPSL. Overall, six mutations were detected: four missense mutations, one in-frame deletion, and one splice-site mutation. Our assumption is that DHDPSL is the gene encoding 4-hydroxy-2-oxoglutarate aldolase, catalyzing the final step in the metabolic pathway of hydroxyproline.

Truncating mutations in the chloride/proton ClC-5 antiporter gene in Seven Jewish Israeli families with Dent's 1 disease.

Dent's disease is an X-linked hereditary renal tubular disorder characterized by low-molecular-weight proteinuria (LMWP), hypercalciuria, nephrocalcinosis, nephrolithiasis, rickets and progressive renal failure. About 60% of patients have mutations in the CLCN5 gene (Dent 1), which encodes a kidney-specific chloride/proton antiporter, and 15% of patients have mutations in the OCRL1 gene (Dent 2). The aim of the study was to identify CLCN5 mutations in Jewish Israeli families with Dent's disease and to characterize the associated clinical syndromes. We studied 17 patients from 14 unrelated Israeli families with a clinical diagnosis of Dent's disease. LMWP was detected in all patients. Most of the affected individuals had hypercalciuria and nephrocalcinosis. Renal stones were found in 1 patient, and renal insufficiency developed in 2 patients. We identified six different truncating CLCN5 mutations that were segregated with the disease in 7 families: three nonsense mutations (Arg28stop, Arg467stop and Arg637stop), one deletion mutation (505delA) and two novel mutations, consisted of one deletion mutation (1493delG) and one insertion mutation (409insC). All the mutations cause premature termination of protein translation and result in a non-functional truncated protein. The clinical characteristics of patients with different mutations were, in general, similar.