Effects of rare kidney diseases on kidney failure: a longitudinal analysis of the UK National Registry of Rare Kidney Diseases (RaDaR) cohort.

BACKGROUND: Individuals with rare kidney diseases account for 5-10% of people with chronic kidney disease, but constitute more than 25% of patients receiving kidney replacement therapy. The National Registry of Rare Kidney Diseases (RaDaR) gathers longitudinal data from patients with these conditions, which we used to study disease progression and outcomes of death and kidney failure. METHODS: People aged 0-96 years living with 28 types of rare kidney diseases were recruited from 108 UK renal care facilities. The primary outcomes were cumulative incidence of mortality and kidney failure in individuals with rare kidney diseases, which were calculated and compared with that of unselected patients with chronic kidney disease. Cumulative incidence and Kaplan-Meier survival estimates were calculated for the following outcomes: median age at kidney failure; median age at death; time from start of dialysis to death; and time from diagnosis to estimated glomerular filtration rate (eGFR) thresholds, allowing calculation of time from last eGFR of 75 mL/min per 1·73 m2 or more to first eGFR of less than 30 mL/min per 1·73 m2 (the therapeutic trial window). FINDINGS: Between Jan 18, 2010, and July 25, 2022, 27 285 participants were recruited to RaDaR. Median follow-up time from diagnosis was 9·6 years (IQR 5·9-16·7). RaDaR participants had significantly higher 5-year cumulative incidence of kidney failure than 2·81 million UK patients with all-cause chronic kidney disease (28% vs 1%; p<0·0001), but better survival rates (standardised mortality ratio 0·42 [95% CI 0·32-0·52]; p<0·0001). Median age at kidney failure, median age at death, time from start of dialysis to death, time from diagnosis to eGFR thresholds, and therapeutic trial window all varied substantially between rare diseases. INTERPRETATION: Patients with rare kidney diseases differ from the general population of individuals with chronic kidney disease: they have higher 5-year rates of kidney failure but higher survival than other patients with chronic kidney disease stages 3-5, and so are over-represented in the cohort of patients requiring kidney replacement therapy. Addressing unmet therapeutic need for patients with rare kidney diseases could have a large beneficial effect on long-term kidney replacement therapy demand. FUNDING: RaDaR is funded by the Medical Research Council, Kidney Research UK, Kidney Care UK, and the Polycystic Kidney Disease Charity.

A Neanderthal haplotype introgressed into the human genome confers protection against membranous nephropathy.

Class 2 HLA and PLA2R1 alleles are exceptionally strong genetic risk factors for membranous nephropathy (MN), leading, through an unknown mechanism, to a targeted autoimmune response. Introgressed archaic haplotypes (introduced from an archaic human genome into the modern human genome) might influence phenotypes through gene dysregulation. Here, we investigated the genomic region surrounding the PLA2R1 gene. We reconstructed the phylogeny of Neanderthal and modern haplotypes in this region and calculated the probability of the observed clustering being the result of introgression or common descent. We imputed variants for the participants in our previous genome-wide association study and we compared the distribution of Neanderthal variants between MN cases and controls. The region associated with the lead MN risk locus in the PLA2R1 gene was confirmed and showed that, within a 507 kb region enriched in introgressed sequence, a stringently defined 105 kb haplotype, intersecting the coding regions for PLA2R1 and ITGB6, is inherited from Neanderthals. Thus, introgressed Neanderthal haplotypes overlapping PLA2R1 are differentially represented in MN cases and controls, with enrichment In controls suggesting a protective effect.

Antenatal presentation and early postnatal treatment of infantile hypercalcemia type 2.

Infantile hypercalcemia (IH) is a rare genetic disorder characterized by hypercalcemia, hypercalciuria, low parathyroid hormone, and nephrocalcinosis during the first months of life. Biallelic variants in the genes CYP24A1 and SCL34A1 cause IH1 and 2, respectively. We present the case of a newborn with an antenatal diagnosis of IH2 due to the identification of echogenic, yet normal-sized kidneys at 23 weeks gestation. Trio whole-exome sequencing initially identified only a heterozygous pathogenic variant in SLC34A1. Re-analysis of the exome data because of the clinical suspicion of IH2 revealed a 21-basepair deletion in trans that had initially been filtered out because of its high allele frequency. The diagnosis of IH2 enabled postnatal screening for hypercalcemia, present already at week 1, resulting in early treatment with phosphate supplementation and vitamin D avoidance. In the subsequent course, biochemical parameters were normalized, and the patient showed no obvious clinical complications of IH2, apart from the nephrocalcinosis.

Tolvaptan and urea in paediatric hyponatraemia.

BACKGROUND: The syndrome of inappropriate antidiuretic hormone (SIADH) is usually treated with fluid restriction. This can be challenging in patients with obligate fluid intake for nutrition or medication. Pharmaceutical treatment with tolvaptan and urea is available but minimal paediatric data are available. We review the efficacy and safety of tolvaptan and urea in paediatric patients with SIADH. METHODS: Retrospective review of paediatric inpatients with clinical diagnosis of SIADH. Patients were identified from pharmacy records based on tolvaptan and urea prescriptions. Relevant information was extracted from patient electronic records. The main outcome measures included the number of days to sodium normalisation, the daily change in plasma sodium concentration, and the maximum increase of plasma sodium concentration in 24 h. Reported side effects were captured. RESULTS: Thirteen patients received tolvaptan and six urea. Five patients had both agents (tolvaptan converted to urea). Tolvaptan led to plasma sodium normalisation in 10/13 (77%) within 6 days (median 2.5 days, range [1, 6]), with a median change of sodium concentration of 7 mmol/L (- 1, 14) within the first 24 h of treatment. Three patients experienced a change in plasma sodium > 10 mmol/l/day but had no apparent side effects. Urea led to sodium normalisation in 5/6 (83%) patients. The median number of days to normalisation with urea was 2 (1, 10) with a median change of plasma sodium concentration of 2 mmol/L (- 1, 6) within the first 24 h. All patients tolerated tolvaptan and/or urea without unexpected side effects. CONCLUSIONS: Tolvaptan and urea appear to be safe and effective when fluid restriction is challenging in paediatric SIADH. A higher resolution version of the Graphical abstract is available as Supplementary information.

Challenges in using fractional excretion of sodium in the assessment of salt poisoning.

AIM: Hypernatraemia typically reflects dehydration, yet in rare instances may be caused by salt poisoning. Identifying these rare cases is a difficult challenge. Making the diagnosis of salt poisoning can have severe consequences, such as the removal of the child from its home or even prison sentences for the implicated carer. It is therefore imperative to get the diagnosis right. Guidelines for the assessment of hypernatraemia emphasise the importance of the fractional excretion of sodium to distinguish between dehydration and salt poisoning, but no generally accepted cut-off value exists. Opinions about the diagnosis of salt poisoning in some cases consequently may differ. Here, we aim to highlight the challenges and stimulate discussion on how to improve the tools for the assessment of hypernatraemia. METHODS: Report of a case of unexplained hypernatraemia in which the treating paediatrician raised the suspicion of salt poisoning. RESULTS: Two consulted experts made opposing judgements about the aetiology of the observed hypernatraemia. CONCLUSION: Clear diagnostic criteria for the diagnosis of salt poisoning are lacking and more data are needed for their establishment. Without this, victims may experience further harm and carers are at risk of devastating, yet potentially erroneous accusations.

Rare variants in the sodium-dependent phosphate transporter gene SLC34A3 explain missing heritability of urinary stone disease.

Urinary stone disease (USD) is a major health burden affecting over 10% of the United Kingdom population. While stone disease is associated with lifestyle, genetic factors also strongly contribute. Common genetic variants at multiple loci from genome-wide association studies account for 5% of the estimated 45% heritability of the disorder. Here, we investigated the extent to which rare genetic variation contributes to the unexplained heritability of USD. Among participants of the United Kingdom 100,000-genome project, 374 unrelated individuals were identified and assigned diagnostic codes indicative of USD. Whole genome gene-based rare variant testing and polygenic risk scoring against a control population of 24,930 ancestry-matched controls was performed. We observed (and replicated in an independent dataset) exome-wide significant enrichment of monoallelic rare, predicted damaging variants in the SLC34A3 gene for a sodium-dependent phosphate transporter that were present in 5% cases compared with 1.6% of controls. This gene was previously associated with autosomal recessive disease. The effect on USD risk of having a qualifying SLC34A3 variant was greater than that of a standard deviation increase in polygenic risk derived from GWAS. Addition of the rare qualifying variants in SLC34A3 to a linear model including polygenic score increased the liability-adjusted heritability from 5.1% to 14.2% in the discovery cohort. We conclude that rare variants in SLC34A3 represent an important genetic risk factor for USD, with effect size intermediate between the fully penetrant rare variants linked with Mendelian disorders and common variants associated with USD. Thus, our findings explain some of the heritability unexplained by prior common variant genome-wide association studies.

Phosphomannomutase 2 (PMM2) variants leading to hyperinsulinism-polycystic kidney disease are associated with early-onset inflammatory bowel disease and gastric antral foveolar hyperplasia.

Phosphomannomutase 2 (PMM2) deficiency causes Congenital Disorder of Glycosylation (PMM2-CDG), but does not have a recognised association with Inflammatory Bowel Disease (IBD). A distinct clinical syndrome of hyperinsulinism and autosomal recessive polycystic kidney disease (HIPKD) arises in the context of a specific variant in the PMM2 promotor, either in homozygosity, or compound heterozygous with a deleterious PMM2 variant. Here, we describe the development of IBD in three patients with PMM2-HIPKD, with onset of IBD at 0, 6, and 10 years of age. In each case, intestinal inflammation coincided with the unusual finding of gastric antral foveolar hyperplasia. IBD disease was of variable severity at onset but well controlled with conventional and first-line biologic treatment approaches. The organ-level pattern of disease manifestations in PMM2-HIPKD-IBD may reflect a loss of cis-acting regulatory control by hepatocyte nuclear factor 4 alpha (HNF4A). Analysis of published transcriptomic data suggests that IBD most likely arises due to an impact on epithelial cellular function. We identify a specific pattern of variation in PMM2 as a novel association of early-onset IBD with distinctive gastric pathology.

Clinical and genetic characteristics of Dent's disease type 1 in Europe.

BACKGROUND: Dent's disease type 1 (DD1) is a rare X-linked nephropathy caused by CLCN5 mutations, characterized by proximal tubule dysfunction, including low molecular weight proteinuria (LMWP), hypercalciuria, nephrolithiasis-nephrocalcinosis, progressive chronic kidney disease (CKD) and kidney failure (KF). Current management is symptomatic and does not prevent disease progression. Here we describe the contemporary DD1 picture across Europe to highlight its unmet needs. METHODS: A physician-based anonymous international e-survey supported by several European nephrology networks/societies was conducted. Questions focused on DD1 clinical features, diagnostic procedure and mutation spectra. RESULTS: A total of 207 DD1 male patients were reported; clinical data were available for 163 with confirmed CLCN5 mutations. Proteinuria was the most common manifestation (49.1%). During follow-up, all patients showed LMWP, 66.4% nephrocalcinosis, 44.4% hypercalciuria and 26.4% nephrolithiasis. After 5.5 years, ≈50% of patients presented with renal dysfunction, 20.7% developed CKD stage ≥3 and 11.1% developed KF. At the last visit, hypercalciuria was more frequent in paediatric patients than in adults (73.4% versus 19.0%). Conversely, nephrolithiasis, nephrocalcinosis and renal dysfunction were more prominent in adults. Furthermore, CKD progressed with age. Despite no clear phenotype/genotype correlation, decreased glomerular filtration rate was more frequent in subjects with CLCN5 mutations affecting the pore or CBS domains compared with those with early-stop mutations. CONCLUSIONS: Results from this large DD1 cohort confirm previous findings and provide new insights regarding age and genotype impact on CKD progression. Our data strongly support that DD1 should be considered in male patients with CKD, nephrocalcinosis/hypercalciuria and non-nephrotic proteinuria and provide additional support for new research opportunities.

Outcome of infantile nephropathic cystinosis depends on early intervention, not genotype: A multicenter sibling cohort study.

Infantile nephropathic cystinosis (INC) is an inheritable lysosomal storage disorder characterized by lysosomal cystine accumulation, progressive kidney disease, and multiple extrarenal complications (ERCs). Cysteamine postpones the onset of end-stage kidney disease (ESKD) and reduces the incidence of ERCs; however, cysteamine is generally initiated upon establishment of the renal Fanconi syndrome (FS) and partial loss of kidney function, whereas data on long-term effects of cysteamine administered from neonatal age are lacking. An international multicenter retrospective cohort study of siblings with INC was set up to investigate the outcome in relation to age at initiation of cysteamine versus CTNS genotype, with attention to patients treated with cysteamine from neonatal age. None of the siblings treated from neonatal age (n = 9; age 10 ± 6 years) had reached ESKD, while 22% of their index counterparts (n = 9; age 14 ± 5 years) had commenced renal replacement therapy. Siblings treated with cysteamine from the onset of symptoms at a younger age compared with their index counterparts, reached ESKD at a significant older age (13 ± 3 vs. 10 ± 3 years, p = 0.002). In contrast, no significant difference in ERCs was observed between sibling and index patients, independently from the age at initiation of cysteamine. The CTNS genotype had no impact on the overall outcome in this cohort. In INC, presymptomatic treatment with cysteamine results in a better renal outcome in comparison to treatment initiated from the onset of symptoms. This justifies including cystinosis into newborn screening programs. SYNOPSIS: In infantile nephropathic cystinosis, presymptomatic treatment with cysteamine improves the renal outcome which justifies the inclusion of cystinosis into newborn screening programs.

Mendelian steroid resistant nephrotic syndrome in childhood: is it as common as reported?

BACKGROUND: Primary steroid resistant nephrotic syndrome (SRNS) is thought to have either genetic or immune-mediated aetiology. Knowing which children to screen for genetic causes can be difficult. Several studies have described the prevalence of genetic causes of primary SRNS to be between 30 and 40%, but these may reflect a selection bias for genetic testing in children with congenital, infantile, syndromic or familial NS and thus may overestimate the true prevalence in a routine clinical setting. METHODS: Retrospective electronic patient record analysis was undertaken of all children with non-syndromic SRNS and presentation beyond the first year of life, followed at our centre between 2005 and 2020. RESULTS: Of the 49 children who met the inclusion criteria, 5 (10%) had causative variants identified, predominantly in NPHS2. None responded to immunosuppression. Of the 44 (90%) who had no genetic cause identified, 33 (75%) had complete or partial remission after commencing second-line immunosuppression and 67% of these had eGFR > 90 ml/min/1.73 m2 at last clinical follow-up. Of the children who did not respond to immunosuppression, 64% progressed to kidney failure. CONCLUSIONS: In our cohort of children with non-syndromic primary SRNS and presentation beyond the first year of life, we report a prevalence of detectable causative genetic variants of 10%. Those with identified genetic cause were significantly (p = 0.003) less likely to respond to immunosuppression and more likely (p = 0.026) to progress to chronic kidney disease. Understanding the genetics along with response to immunosuppression informs management in this cohort of patients and variant interpretation. A higher resolution version of the Graphical abstract is available as Supplementary information.

Shared genetic risk across different presentations of gene test-negative idiopathic nephrotic syndrome.

BACKGROUND: Idiop athic nephrotic syndrome (INS) is classified in children according to response to initial corticosteroid therapy into steroid-sensitive (SSNS) and steroid-resistant nephrotic syndrome (SRNS), and in adults according to histology into minimal change disease (MCD) and focal segmental glomerulosclerosis (FSGS). However, there is well-recognised phenotypic overlap between these entities. Genome-wide association studies (GWAS) have shown a strong association between SSNS and variation at HLA, suggesting an underlying immunological basis. We sought to determine whether a risk score generated from genetic variants associated with SSNS could be used to gain insight into the pathophysiology of INS presenting in other ways. METHODS: We developed an SSNS genetic risk score (SSNS-GRS) from the five variants independently associated with childhood SSNS in a previous European GWAS. We quantified SSNS-GRS in independent cohorts of European individuals with childhood SSNS, non-monogenic SRNS, MCD, and FSGS, and contrasted them with SSNS-GRS quantified in individuals with monogenic SRNS, membranous nephropathy (a different immune-mediated disease-causing nephrotic syndrome), and healthy controls. RESULTS: The SSNS-GRS was significantly elevated in cohorts with SSNS, non-monogenic SRNS, MCD, and FSGS compared to healthy participants and those with membranous nephropathy. The SSNS-GRS in all cohorts with non-monogenic INS were also significantly elevated compared to those with monogenic SRNS. CONCLUSIONS: The shared genetic risk factors among patients with different presentations of INS strongly suggests a shared autoimmune pathogenesis when monogenic causes are excluded. Use of the SSNS-GRS, in addition to testing for monogenic causes, may help to classify patients presenting with INS. A higher resolution version of the Graphical abstract is available as Supplementary information.

Child and caregiver perspectives on access to psychosocial and educational support in pediatric chronic kidney disease: a focus group study.

BACKGROUND: Children with chronic kidney disease (CKD) generally have worse educational and psychosocial outcomes compared with their healthy peers. This can impair their ability to manage their treatment, which in turn can have long-term health consequences through to adulthood. We attempted to capture the experiences of children with CKD and to describe the perspectives of their parents and caregivers on access to educational and psychosocial support. METHODS: Children with CKD (n = 34) and their caregivers (n = 62) were sampled via focus groups from pediatric hospitals in Australia, Canada, and the USA. Sixteen focus groups were convened and the transcripts were analyzed thematically. RESULTS: We identified four themes: disruption to self-esteem and identity (emotional turmoil of adolescence, wrestling with the sick self, powerlessness to alleviate child's suffering, balancing normality and protection); disadvantaged by lack of empathy and acceptance (alienated by ignorance, bearing the burden alone); a hidden and inaccessible support system (excluded from formal psychological support, falling behind due to being denied special considerations); and building resilience (finding partners in the journey, moving towards acceptance of the illness, re-establishing childhood). CONCLUSIONS: Children with CKD and their caregivers encountered many barriers in accessing psychosocial and educational support and felt extremely disempowered and isolated as a consequence. Improved availability and access to psychosocial and educational interventions are needed to improve the wellbeing and educational advancement of children with CKD. A higher resolution version of the Graphical abstract is available as Supplementary information.

Pseudouridylation defect due to DKC1 and NOP10 mutations causes nephrotic syndrome with cataracts, hearing impairment, and enterocolitis.

RNA modifications play a fundamental role in cellular function. Pseudouridylation, the most abundant RNA modification, is catalyzed by the H/ACA small ribonucleoprotein (snoRNP) complex that shares four core proteins, dyskerin (DKC1), NOP10, NHP2, and GAR1. Mutations in DKC1, NOP10, or NHP2 cause dyskeratosis congenita (DC), a disorder characterized by telomere attrition. Here, we report a phenotype comprising nephrotic syndrome, cataracts, sensorineural deafness, enterocolitis, and early lethality in two pedigrees: males with DKC1 p.Glu206Lys and two children with homozygous NOP10 p.Thr16Met. Females with heterozygous DKC1 p.Glu206Lys developed cataracts and sensorineural deafness, but nephrotic syndrome in only one case of skewed X-inactivation. We found telomere attrition in both pedigrees, but no mucocutaneous abnormalities suggestive of DC. Both mutations fall at the dyskerin-NOP10 binding interface in a region distinct from those implicated in DC, impair the dyskerin-NOP10 interaction, and disrupt the catalytic pseudouridylation site. Accordingly, we found reduced pseudouridine levels in the ribosomal RNA (rRNA) of the patients. Zebrafish dkc1 mutants recapitulate the human phenotype and show reduced 18S pseudouridylation, ribosomal dysregulation, and a cell-cycle defect in the absence of telomere attrition. We therefore propose that this human disorder is the consequence of defective snoRNP pseudouridylation and ribosomal dysfunction.

Gitelman-Like Syndrome Caused by Pathogenic Variants in mtDNA.

BACKGROUND: Gitelman syndrome is the most frequent hereditary salt-losing tubulopathy characterized by hypokalemic alkalosis and hypomagnesemia. Gitelman syndrome is caused by biallelic pathogenic variants in SLC12A3, encoding the Na+-Cl- cotransporter (NCC) expressed in the distal convoluted tubule. Pathogenic variants of CLCNKB, HNF1B, FXYD2, or KCNJ10 may result in the same renal phenotype of Gitelman syndrome, as they can lead to reduced NCC activity. For approximately 10 percent of patients with a Gitelman syndrome phenotype, the genotype is unknown. METHODS: We identified mitochondrial DNA (mtDNA) variants in three families with Gitelman-like electrolyte abnormalities, then investigated 156 families for variants in MT-TI and MT-TF, which encode the transfer RNAs for phenylalanine and isoleucine. Mitochondrial respiratory chain function was assessed in patient fibroblasts. Mitochondrial dysfunction was induced in NCC-expressing HEK293 cells to assess the effect on thiazide-sensitive 22Na+ transport. RESULTS: Genetic investigations revealed four mtDNA variants in 13 families: m.591C>T (n=7), m.616T>C (n=1), m.643A>G (n=1) (all in MT-TF), and m.4291T>C (n=4, in MT-TI). Variants were near homoplasmic in affected individuals. All variants were classified as pathogenic, except for m.643A>G, which was classified as a variant of uncertain significance. Importantly, affected members of six families with an MT-TF variant additionally suffered from progressive chronic kidney disease. Dysfunction of oxidative phosphorylation complex IV and reduced maximal mitochondrial respiratory capacity were found in patient fibroblasts. In vitro pharmacological inhibition of complex IV, mimicking the effect of the mtDNA variants, inhibited NCC phosphorylation and NCC-mediated sodium uptake. CONCLUSION: Pathogenic mtDNA variants in MT-TF and MT-TI can cause a Gitelman-like syndrome. Genetic investigation of mtDNA should be considered in patients with unexplained Gitelman syndrome-like tubulopathies.

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.

Perspectives of Clinicians on Shared Decision Making in Pediatric CKD: A Qualitative Study.

RATIONALE & OBJECTIVE: Clinical decision-making priorities may differ among children, their parents, and their clinicians. This study describes clinicians' perspectives on shared decision making in pediatric chronic kidney disease (CKD) and identifies opportunities to improve shared decision making and care for children with CKD and their families. STUDY DESIGN: Semistructured interviews. SETTING & PARTICIPANTS: Fifty clinicians participated, including pediatric nephrologists, nurses, social workers, surgeons, dietitians, and psychologists involved in providing care to children with CKD. They worked at 18 hospitals and 4 university research departments across 11 countries (United States of America, Canada, Australia, People's Republic of China, United Kingdom, Germany, France, Italy, Lithuania, New Zealand, and Singapore). ANALYTICAL APPROACH: Interview transcripts were analyzed thematically. RESULTS: We identified 4 themes: (1) striving to blend priorities (minimizing treatment burden, emphasizing clinical long-term risks, achieving common goals), (2) focusing on medical responsibilities (carrying decisional burden and pressure of expectations, working within system constraints, ensuring safety is foremost concern), (3) collaborating to achieve better long-term outcomes (individualizing care, creating partnerships, encouraging ownership and participation in shared decision making, sensitive to parental distress), and (4) forming cumulative knowledge (balancing reassurance and realistic expectations, building understanding around treatment, harnessing motivation for long-term goals). LIMITATIONS: Most clinicians were from high-income countries, so the transferability of the findings to other settings is uncertain. CONCLUSIONS: Clinicians reported striving to minimize treatment burden and working with children and their families to manage their expectations and support their decision making. However, they are challenged with system constraints and sometimes felt the pressure of being responsible for the child's long-term outcomes. Further studies are needed to test whether support for shared decision making would promote strategies to establish and improve the quality of care for children with CKD.

Patient and caregiver perspectives on blood pressure in children with chronic kidney disease.

BACKGROUND: More than 50% of children with chronic kidney disease (CKD) have uncontrolled hypertension, increasing their long-term risk of cardiovascular disease and progression to kidney failure. Children receiving medications or dialysis may also experience acute blood pressure fluctuations accompanied by debilitating symptoms. We aimed to describe the perspectives of children with CKD and their parental caregivers on blood pressure to inform patient-centered care. METHODS: Secondary thematic analysis was conducted on qualitative data from the Standardized Outcomes in Nephrology-Children and Adolescents initiative, encompassing 16 focus groups, an international Delphi survey and two consensus workshops. We analyzed responses from children with CKD (ages 8-21 years) and caregivers (of children ages 0-21 years) pertaining to blood pressure. RESULTS: Overall, 120 patients and 250 caregivers from 22 countries participated. We identified five themes: invisibility and normalization (reassured by apparent normotension, absence of symptoms and expected links with CKD), confused by ambiguity (hypertension indistinguishable from cardiovascular disease, questioning the need for prophylactic intervention, frustrated by inconsistent messages and struggling with technical skills in measurement), enabling monitoring and maintaining health (gaging well-being and preventing vascular complications), debilitating and constraining daily living (provoking anxiety and agitation, helpless and powerless and limiting life activities) and burden of medications (overwhelmed by the quantity of tablets and distress from unexpected side effects). CONCLUSIONS: For children with CKD and their caregivers, blood pressure was an important heath indicator, but uncertainty around its implications and treatment hampered management. Providing educational resources to track blood pressure and minimizing symptoms and treatment burden may improve outcomes in children with CKD.

Whole-exome sequencing and variant spectrum in children with suspected inherited renal tubular disorder: the East India Tubulopathy Gene Study.

BACKGROUND: Inherited tubulopathies are a heterogeneous group of genetic disorders making whole-exome sequencing (WES) the preferred diagnostic methodology. METHODS: This was a multicenter descriptive study wherein children (< 18 years) with clinically suspected tubular disorders were recruited for molecular testing through WES. Multiplex ligation-dependent probe amplification (MLPA) and Sanger sequencing were done when required. Variants were classified as per American College of Medical Genetics 2015 guidelines and pathogenic (P)/likely pathogenic (LP) variants were considered causative. RESULTS: There were 77 index cases (male =73%). Median age at diagnosis was 48 months (IQR 18.5 to 108 months). At recruitment, the number of children in each clinical group was as follows: distal renal tubular acidosis (dRTA) = 25; Bartter syndrome = 18; isolated hypophosphatemic rickets (HP) = 6; proximal tubular dysfunction (pTD) = 12; nephrogenic diabetes insipidus (NDI) = 6; kidney stone/nephrocalcinosis (NC) = 6; others = 4. We detected 55 (24 novel) P/LP variants, providing genetic diagnoses in 54 children (70%). The diagnostic yield of WES was highest for NDI (100%), followed by HP (83%; all X-linked HP), Bartter syndrome (78%), pTD (75%), dRTA (64%), and NC (33%). Molecular testing had a definite impact on clinical management in 24 (31%) children. This included revising clinical diagnosis among 14 children (26% of those with a confirmed genetic diagnosis and 18% of the overall cohort), detection of previously unrecognized co-morbidities among 8 children (sensorineural deafness n = 5, hemolytic anemia n = 2, and dental changes n = 1) and facilitating specific medical treatment for 7 children (primary hyperoxaluria n = 1, cystinosis n = 4, tyrosinemia n = 2). CONCLUSION: WES is a powerful tool in the diagnosis and management of children with inherited tubulopathies in the Indian population. A higher resolution version of the Graphical abstract is available as Supplementary information.

Long-term kidney function in children with Wilms tumour and constitutional WT1 pathogenic variant.

BACKGROUND: Wilms tumour (WT) survivors, especially patients with associated syndromes or genitourinary anomalies due to constitutional WT1 pathogenic variant, have increased risk of kidney failure. We describe the long-term kidney function in children with WT and WT1 pathogenic variant to inform the surgical strategy and oncological management of such complex children. METHODS: Retrospective analysis of patients with WT and constitutional WT1 pathogenic variant treated at a single centre between 1993 and 2016, reviewing genotype, phenotype, tumour histology, laterality, treatment, patient survival, and kidney outcome. RESULTS: We identified 25 patients (60% male, median age at diagnosis 14 months, range 4-74 months) with WT1 deletion (4), missense (2), nonsense (8), frameshift (7), or splice site (4) pathogenic variant. Thirteen (52%) had bilateral disease, 3 (12%) had WT-aniridia, 1 had incomplete Denys-Drash syndrome, 11 (44%) had genitourinary malformation, and 10 (40%) had no phenotypic anomalies. Patient survival was 100% and 3 patients were in remission after relapse at median follow-up of 9 years. Seven patients (28%) commenced chronic dialysis of which 3 were after bilateral nephrectomies. The overall kidney survival for this cohort as mean time to start of dialysis was 13.38 years (95% CI: 10.3-16.4), where 7 patients experienced kidney failure at a median of 5.6 years. All of these 7 patients were subsequently transplanted. In addition, 2 patients have stage III and stage IV chronic kidney disease and 12 patients have albuminuria and/or treatment with ACE inhibitors. Four patients (3 frameshift; 1 WT1 deletion) had normal blood pressure and kidney function without proteinuria at follow-up from 1.5 to 12 years. CONCLUSIONS: Despite the known high risk of kidney disease in patients with WT and constitutional WT1 pathogenic variant, nearly two-thirds of patients had sustained native kidney function, suggesting that nephron-sparing surgery (NSS) should be attempted when possible without compromising oncological risk. Larger international studies are needed for accurate assessment of WT1genotype-kidney function phenotype correlation.