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Most patients with rare diseases do not receive a molecular diagnosis and the aetiological variants and causative genes for more than half such disorders remain to be discovered1. Here we used whole-genome sequencing (WGS) in a national health system to streamline diagnosis and to discover unknown aetiological variants in the coding and non-coding regions of the genome. We generated WGS data for 13,037 participants, of whom 9,802 had a rare disease, and provided a genetic diagnosis to 1,138 of the 7,065 extensively phenotyped participants. We identified 95 Mendelian associations between genes and rare diseases, of which 11 have been discovered since 2015 and at least 79 are confirmed to be aetiological. By generating WGS data of UK Biobank participants2, we found that rare alleles can explain the presence of some individuals in the tails of a quantitative trait for red blood cells. Finally, we identified four novel non-coding variants that cause disease through the disruption of transcription of ARPC1B, GATA1, LRBA and MPL. Our study demonstrates a synergy by using WGS for diagnosis and aetiological discovery in routine healthcare.
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Internacionalidad , Programas Nacionales de Salud , Enfermedades Raras/diagnóstico , Enfermedades Raras/genética , Secuenciación Completa del Genoma , Complejo 2-3 Proteico Relacionado con la Actina/genética , Proteínas Adaptadoras Transductoras de Señales/genética , Alelos , Bases de Datos Factuales , Eritrocitos/metabolismo , Factor de Transcripción GATA1/genética , Humanos , Fenotipo , Sitios de Carácter Cuantitativo , Receptores de Trombopoyetina/genética , Medicina Estatal , Reino UnidoRESUMEN
Focal segmental glomerulosclerosis (FSGS) is the main pathology underlying steroid-resistant nephrotic syndrome (SRNS) and a leading cause of chronic kidney disease. Monogenic forms of pediatric SRNS are predominantly caused by recessive mutations, while the contribution of de novo variants (DNVs) to this trait is poorly understood. Using exome sequencing (ES) in a proband with FSGS/SRNS, developmental delay, and epilepsy, we discovered a nonsense DNV in TRIM8, which encodes the E3 ubiquitin ligase tripartite motif containing 8. To establish whether TRIM8 variants represent a cause of FSGS, we aggregated exome/genome-sequencing data for 2,501 pediatric FSGS/SRNS-affected individuals and 48,556 control subjects, detecting eight heterozygous TRIM8 truncating variants in affected subjects but none in control subjects (p = 3.28 × 10-11). In all six cases with available parental DNA, we demonstrated de novo inheritance (p = 2.21 × 10-15). Reverse phenotyping revealed neurodevelopmental disease in all eight families. We next analyzed ES from 9,067 individuals with epilepsy, yielding three additional families with truncating TRIM8 variants. Clinical review revealed FSGS in all. All TRIM8 variants cause protein truncation clustering within the last exon between residues 390 and 487 of the 551 amino acid protein, indicating a correlation between this syndrome and loss of the TRIM8 C-terminal region. Wild-type TRIM8 overexpressed in immortalized human podocytes and neuronal cells localized to nuclear bodies, while constructs harboring patient-specific variants mislocalized diffusely to the nucleoplasm. Co-localization studies demonstrated that Gemini and Cajal bodies frequently abut a TRIM8 nuclear body. Truncating TRIM8 DNVs cause a neuro-renal syndrome via aberrant TRIM8 localization, implicating nuclear bodies in FSGS and developmental brain disease.
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Proteínas Portadoras/genética , Discapacidades del Desarrollo/genética , Epilepsia/genética , Glomeruloesclerosis Focal y Segmentaria/genética , Espacio Intranuclear/metabolismo , Síndrome Nefrótico/genética , Síndrome Nefrótico/metabolismo , Proteínas del Tejido Nervioso/genética , Adulto , Animales , Proteínas Portadoras/química , Proteínas Portadoras/metabolismo , Línea Celular , Niño , Preescolar , Codón sin Sentido , Discapacidades del Desarrollo/metabolismo , Epilepsia/metabolismo , Femenino , Glomeruloesclerosis Focal y Segmentaria/metabolismo , Humanos , Riñón/metabolismo , Masculino , Ratones , Mutación , Proteínas del Tejido Nervioso/química , Proteínas del Tejido Nervioso/metabolismo , Fenotipo , Podocitos/metabolismo , Secuenciación del ExomaRESUMEN
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.
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Glomerulonefritis Membranosa , Glomeruloesclerosis Focal y Segmentaria , Nefrosis Lipoidea , Síndrome Nefrótico , Niño , Humanos , Síndrome Nefrótico/diagnóstico , Síndrome Nefrótico/tratamiento farmacológico , Síndrome Nefrótico/genética , Nefrosis Lipoidea/diagnóstico , Nefrosis Lipoidea/tratamiento farmacológico , Nefrosis Lipoidea/genética , Glomeruloesclerosis Focal y Segmentaria/diagnóstico , Glomeruloesclerosis Focal y Segmentaria/tratamiento farmacológico , Glomeruloesclerosis Focal y Segmentaria/genética , Estudio de Asociación del Genoma Completo , Esteroides , Factores de RiesgoRESUMEN
Steroid-resistant nephrotic syndrome (SRNS) is characterized by high-range proteinuria and most often focal and segmental glomerulosclerosis (FSGS). Identification of mutations in genes causing SRNS has improved our understanding of disease mechanisms and highlighted defects in the podocyte, a highly specialized glomerular epithelial cell, as major factors in disease pathogenesis. By exome sequencing, we identified missense mutations in TBC1D8B in two families with an X-linked early-onset SRNS with FSGS. TBC1D8B is an uncharacterized Rab-GTPase-activating protein likely involved in endocytic and recycling pathways. Immunofluorescence studies revealed TBC1D8B presence in human glomeruli, and affected individual podocytes displayed architectural changes associated with migration defects commonly found in FSGS. In zebrafish we demonstrated that both knockdown and knockout of the unique TBC1D8B ortholog-induced proteinuria and that this phenotype was rescued by human TBC1D8B mRNA injection, but not by either of the two mutated mRNAs. We also showed an interaction between TBC1D8B and Rab11b, a key protein in vesicular recycling in cells. Interestingly, both internalization and recycling processes were dramatically decreased in affected individuals' podocytes and fibroblasts, confirming the crucial role of TBC1D8B in the cellular recycling processes, probably as a Rab11b GTPase-activating protein. Altogether, these results confirmed that pathogenic variations in TBC1D8B are involved in X-linked podocytopathy and points to alterations in recycling processes as a mechanism of SRNS.
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Proteínas de Unión al Calcio/genética , Enfermedades Genéticas Ligadas al Cromosoma X/genética , Mutación con Pérdida de Función , Síndrome Nefrótico/genética , Proteínas de Transporte Vesicular/genética , Proteínas de Pez Cebra/genética , Animales , Transporte Biológico/genética , Proteínas de Unión al Calcio/metabolismo , Femenino , Fibroblastos/citología , Fibroblastos/metabolismo , Humanos , Glomérulos Renales/metabolismo , Masculino , Podocitos/citología , Podocitos/metabolismo , Proteínas de Transporte Vesicular/metabolismo , Secuenciación del Exoma , Pez Cebra , Proteínas de Pez Cebra/metabolismo , Proteínas de Unión al GTP rab/metabolismoRESUMEN
BACKGROUND: Variants in genes encoding nuclear pore complex (NPC) proteins are a newly identified cause of paediatric steroid-resistant nephrotic syndrome (SRNS). Recent reports describing NUP93 variants suggest these could be a significant cause of paediatric onset SRNS. We report NUP93 cases in the UK and demonstrate in vivo functional effects of Nup93 depletion in a fly (Drosophila melanogaster) nephrocyte model. METHODS: Three hundred thirty-seven paediatric SRNS patients from the National cohort of patients with Nephrotic Syndrome (NephroS) were whole exome and/or whole genome sequenced. Patients were screened for over 70 genes known to be associated with Nephrotic Syndrome (NS). D. melanogaster Nup93 knockdown was achieved by RNA interference using nephrocyte-restricted drivers. RESULTS: Six novel homozygous and compound heterozygous NUP93 variants were detected in 3 sporadic and 2 familial paediatric onset SRNS characterised histologically by focal segmental glomerulosclerosis (FSGS) and progressing to kidney failure by 12 months from clinical diagnosis. Silencing of the two orthologs of human NUP93 expressed in D. melanogaster, Nup93-1, and Nup93-2 resulted in significant signal reduction of up to 82% in adult pericardial nephrocytes with concomitant disruption of NPC protein expression. Additionally, nephrocyte morphology was highly abnormal in Nup93-1 and Nup93-2 silenced flies surviving to adulthood. CONCLUSION: We expand the spectrum of NUP93 variants detected in paediatric onset SRNS and demonstrate its incidence within a national cohort. Silencing of either D. melanogaster Nup93 ortholog caused a severe nephrocyte phenotype, signaling an important role for the nucleoporin complex in podocyte biology. A higher resolution version of the Graphical abstract is available as Supplementary information.
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Drosophila melanogaster , Síndrome Nefrótico , Proteínas de Complejo Poro Nuclear , Podocitos , Adulto , Animales , Niño , Modelos Animales de Enfermedad , Drosophila melanogaster/genética , Resistencia a Medicamentos/genética , Glucocorticoides/efectos adversos , Glucocorticoides/uso terapéutico , Secuenciación de Nucleótidos de Alto Rendimiento , Humanos , Mutación , Síndrome Nefrótico/tratamiento farmacológico , Síndrome Nefrótico/genética , Síndrome Nefrótico/metabolismo , Proteínas de Complejo Poro Nuclear/genética , Podocitos/metabolismoRESUMEN
BACKGROUND: Focal segmental glomerulosclerosis (FSGS) in pediatric patients is typically difficult to treat and will progress to end-stage renal disease (ESRD) in about 10% of cases. Following kidney transplantation, FSGS can recur in up to 56% of renal allografts-with a near 100% recurrence in subsequent transplants. METHODS: Four different pediatric centers across the USA and the UK employed a protocol using LDL-apheresis (LDL-A) and pulse solumedrol to treat recurrent FSGS after transplantation in seven patients. All the patients included in this series demonstrated immediate, or early, recurrence of FSGS, which clinically presented as nephrotic-range proteinuria within hours to days after implantation of the kidney. RESULTS: All patients experienced reductions in urinary protein to creatinine ratios resulting in partial or complete remission. All patients demonstrated improvements in their estimated GFRs at their most recent follow-up since LDL-A discontinuation. CONCLUSIONS: This case series describes the successful treatment, across four different pediatric centers, of seven pediatric patients with recurrent post-transplant FSGS using the Liposorber® LA-15 in combination with pulse solumedrol.
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Eliminación de Componentes Sanguíneos/métodos , Glomeruloesclerosis Focal y Segmentaria/terapia , Trasplante de Riñón , Lipoproteínas LDL/sangre , Hemisuccinato de Metilprednisolona/administración & dosificación , Proteinuria/terapia , Aloinjertos/patología , Niño , Preescolar , Terapia Combinada/métodos , Creatinina/orina , Progresión de la Enfermedad , Femenino , Estudios de Seguimiento , Tasa de Filtración Glomerular , Glomeruloesclerosis Focal y Segmentaria/sangre , Glomeruloesclerosis Focal y Segmentaria/diagnóstico , Glomeruloesclerosis Focal y Segmentaria/patología , Humanos , Lactante , Fallo Renal Crónico/cirugía , Glomérulos Renales/patología , Masculino , Proteinuria/sangre , Proteinuria/diagnóstico , Proteinuria/patología , Quimioterapia por Pulso , Recurrencia , Inducción de Remisión/métodos , Estudios Retrospectivos , Resultado del TratamientoRESUMEN
Nephrotic syndrome (NS), the association of gross proteinuria, hypoalbuminaemia, edema, and hyperlipidemia, can be clinically divided into steroid-sensitive (SSNS) and steroid-resistant (SRNS) forms. SRNS regularly progresses to end-stage renal failure. By homozygosity mapping and whole exome sequencing, we here identify recessive mutations in Crumbs homolog 2 (CRB2) in four different families affected by SRNS. Previously, we established a requirement for zebrafish crb2b, a conserved regulator of epithelial polarity, in podocyte morphogenesis. By characterization of a loss-of-function mutation in zebrafish crb2b, we now show that zebrafish crb2b is required for podocyte foot process arborization, slit diaphragm formation, and proper nephrin trafficking. Furthermore, by complementation experiments in zebrafish, we demonstrate that CRB2 mutations result in loss of function and therefore constitute causative mutations leading to NS in humans. These results implicate defects in podocyte apico-basal polarity in the pathogenesis of NS.
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Proteínas Portadoras/genética , Proteínas de la Membrana/genética , Síndrome Nefrótico/genética , Secuencia de Aminoácidos , Animales , Proteínas Portadoras/metabolismo , Niño , Preescolar , Mapeo Cromosómico , Exoma , Genes Recesivos , Homocigoto , Humanos , Lactante , Fallo Renal Crónico/etiología , Fallo Renal Crónico/genética , Proteínas de la Membrana/metabolismo , Datos de Secuencia Molecular , Mutación , Síndrome Nefrótico/complicaciones , Podocitos , Ratas , Pez Cebra/genéticaRESUMEN
Steroid-resistant nephrotic syndrome (SRNS), a heterogeneous disorder of the renal glomerular filtration barrier, results in impairment of glomerular permselectivity. Inheritance of genetic SRNS may be autosomal dominant or recessive, with a subset of autosomal recessive SRNS presenting as congenital nephrotic syndrome (CNS). Mutations in 53 genes are associated with human SRNS, but these mutations explain ≤30% of patients with hereditary cases and only 20% of patients with sporadic cases. The proteins encoded by these genes are expressed in podocytes, and malfunction of these proteins leads to a universal end point of podocyte injury, glomerular filtration barrier disruption, and SRNS. Here, we identified novel disease-causing mutations in membrane-associated guanylate kinase, WW, and PDZ domain-containing 2 (MAGI2) through whole-exome sequencing of a deeply phenotyped cohort of patients with congenital, childhood-onset SRNS. Although MAGI2 has been shown to interact with nephrin and regulate podocyte cytoskeleton and slit diaphragm dynamics, MAGI2 mutations have not been described in human SRNS. We detected two unique frameshift mutations and one duplication in three patients (two families); two siblings shared the same homozygous frameshift mutation, whereas one individual with sporadic SRNS exhibited compound heterozygosity. Two mutations were predicted to introduce premature stop codons, and one was predicted to result in read through of the normal translational termination codon. Immunohistochemistry in kidney sections from these patients revealed that mutations resulted in lack of or diminished podocyte MAGI2 expression. Our data support the finding that mutations in the MAGI2 gene are causal for congenital SRNS.
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Proteínas Portadoras/genética , Mutación , Síndrome Nefrótico/congénito , Proteínas Adaptadoras Transductoras de Señales , Femenino , Guanilato-Quinasas , Humanos , Lactante , Masculino , Síndrome Nefrótico/genéticaRESUMEN
Steroid Resistant Nephrotic Syndrome (SRNS) in children and young adults has differing etiologies with monogenic disease accounting for 2.9-30% in selected series. Using whole exome sequencing we sought to stratify a national population of children with SRNS into monogenic and non-monogenic forms, and further define those groups by detailed phenotypic analysis. Pediatric patients with SRNS were identified via a national United Kingdom Renal Registry. Whole exome sequencing was performed on 187 patients, of which 12% have a positive family history with a focus on the 53 genes currently known to be associated with nephrotic syndrome. Genetic findings were correlated with individual case disease characteristics. Disease causing variants were detected in 26.2% of patients. Most often this occurred in the three most common SRNS-associated genes: NPHS1, NPHS2, and WT1 but also in 14 other genes. The genotype did not always correlate with expected phenotype since mutations in OCRL, COL4A3, and DGKE associated with specific syndromes were detected in patients with isolated renal disease. Analysis by primary/presumed compared with secondary steroid resistance found 30.8% monogenic disease in primary compared with none in secondary SRNS permitting further mechanistic stratification. Genetic SRNS progressed faster to end stage renal failure, with no documented disease recurrence post-transplantation within this cohort. Primary steroid resistance in which no gene mutation was identified had a 47.8% risk of recurrence. In this unbiased pediatric population, whole exome sequencing allowed screening of all current candidate genes. Thus, deep phenotyping combined with whole exome sequencing is an effective tool for early identification of SRNS etiology, yielding an evidence-based algorithm for clinical management.
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Genómica/métodos , Mutación , Síndrome Nefrótico/congénito , Medicina de Precisión , Adolescente , Edad de Inicio , Niño , Preescolar , Estudios de Cohortes , Progresión de la Enfermedad , Exoma , Femenino , Estudios de Asociación Genética , Predisposición Genética a la Enfermedad , Herencia , Secuenciación de Nucleótidos de Alto Rendimiento , Humanos , Lactante , Péptidos y Proteínas de Señalización Intracelular/genética , Estimación de Kaplan-Meier , Riñón/patología , Fallo Renal Crónico/diagnóstico , Fallo Renal Crónico/genética , Fallo Renal Crónico/terapia , Masculino , Proteínas de la Membrana/genética , Síndrome Nefrótico/diagnóstico , Síndrome Nefrótico/genética , Síndrome Nefrótico/terapia , Linaje , Fenotipo , Valor Predictivo de las Pruebas , Pronóstico , Sistema de Registros , Factores de Riesgo , Reino Unido , Proteínas WT1/genética , Adulto JovenRESUMEN
BACKGROUND: Mutations in podocyte and basement membrane genes are associated with a growing spectrum of glomerular disease affecting adults and children. Investigation of familial cases has helped to build understanding of both normal physiology and disease. METHODS: We investigated a consanguineous family with a wide clinical phenotype of glomerular disease using clinical, histological, and new genetic studies. RESULTS: We report striking variability in severity of nephropathy within an X-linked Alport syndrome (XLAS) family. Four siblings each carried a mutant COL4A5 allele, p.(Gly953Val) and p.(Gly1033Arg). Two boys had signs limited to hematuria and mild/moderate proteinuria. In striking contrast, a sister presented with end-stage renal disease (ESRD) at 8 years of age and an infant brother presented with nephrotic syndrome, progressing to ESRD by 3 years of age. Both were subsequently found to have homozygous variants in MYO1E, p.(Lys118Glu) and p.(Thr876Arg). MYO1E is a gene implicated in focal segmental glomerulosclerosis and it encodes a podocyte-expressed non-muscle myosin. Bioinformatic modeling demonstrated that the collagen IV-alpha3,4,5 extracellular network connected via known protein-protein interactions to intracellular myosin 1E. CONCLUSIONS: COL4A5 and MYO1E mutations may summate to perturb common signaling pathways, resulting in more severe disease than anticipated independently. We suggest screening for MYO1E and other non-COL4 'podocyte gene' mutations in XLAS when clinical nephropathy is more severe than expected for an individual's age and sex.
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Colágeno Tipo IV/genética , Glomérulos Renales/patología , Miosina Tipo I/genética , Nefritis Hereditaria , Adulto , Niño , Preescolar , Femenino , Humanos , Lactante , Patrón de Herencia/genética , Masculino , Mutación , Nefritis Hereditaria/diagnóstico , Nefritis Hereditaria/genética , Nefritis Hereditaria/fisiopatología , Linaje , Índice de Severidad de la Enfermedad , HermanosRESUMEN
Of children with idiopathic nephrotic syndrome, 10%-20% fail to respond to steroids or develop secondary steroid resistance (termed initial steroid sensitivity) and the majority progress to transplantation. Although 30%-50% of these patients suffer disease recurrence after transplantation, with poor long-term outcome, no reliable indicator of recurrence has yet been identified. Notably, the incidence of recurrence after transplantation appears reduced in patients with steroid-resistant nephrotic syndrome (SRNS) due to monogenic disorders. We reviewed 150 transplanted patients with SRNS to identify biomarkers that consistently predict outcome of SRNS after transplantation. In all, 25 children had genetic or familial SRNS and did not experience post-transplant recurrence. We reviewed phenotypic factors, including initial steroid sensitivity, donor type, age, ethnicity, time to ESRD, and time on dialysis, in the remaining 125 children. Of these patients, 57 (45.6%) developed post-transplant recurrence; 26 of 28 (92.9%) patients with initial steroid sensitivity recurred after transplantation, whereas only 26 of 86 (30.2%) patients resistant from the outset recurred (odds ratio, 30; 95% confidence interval, 6.62 to 135.86; P<0.001). We were unable to determine recurrence in two patients (one with initial steroid sensitivity), and nine patients did not receive initial steroids. Our data show that initial steroid sensitivity is highly predictive of post-transplant disease recurrence in this pediatric patient population. Because a pathogenic circulating permeability factor in nephrotic syndrome remains to be confirmed, we propose initial steroid sensitivity as a surrogate marker for post-transplant recurrence.
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Fallo Renal Crónico/tratamiento farmacológico , Fallo Renal Crónico/cirugía , Trasplante de Riñón , Síndrome Nefrótico/tratamiento farmacológico , Síndrome Nefrótico/cirugía , Esteroides/uso terapéutico , Adolescente , Distribución por Edad , Edad de Inicio , Biomarcadores/metabolismo , Niño , Preescolar , Resistencia a Medicamentos , Femenino , Humanos , Lactante , Fallo Renal Crónico/epidemiología , Fallo Renal Crónico/genética , Masculino , Síndrome Nefrótico/epidemiología , Síndrome Nefrótico/genética , Recurrencia , Diálisis Renal , Factores de Riesgo , TranscriptomaRESUMEN
Background: Idiopathic nephrotic syndrome (INS) is a heterogenous disease and current classification is based on observational responses to therapies or kidney histology. The National Unified Renal Translational Research Enterprise (NURTuRE)-INS cohort aims to facilitate novel ways of stratifying INS patients to improve disease understanding, therapeutics and design of clinical trials. Methods: NURTuRE-INS is a prospective cohort study of children and adults with INS in a linked biorepository. All recruits had at least one sampling visit collecting serum, plasma, urine and blood for RNA and DNA extraction, frozen within 2 hours of collection. Clinical histology slides and biopsy tissue blocks were also collected. Results: A total of 739 participants were recruited from 23 centres to NURTuRE-INS, half of whom were diagnosed in childhood [n = 365 (49%)]. The majority were white [n = 525 (71%)] and the median age at recruitment was 32 years (interquartile range 12-54). Steroid-sensitive nephrotic syndrome (SSNS) was the most common clinical diagnosis [n = 518 (70%)]. Of patients diagnosed in childhood who underwent a kidney biopsy, for SSNS (n =103), 76 demonstrated minimal change disease (MCD), whereas for steroid-resistant nephrotic syndrome (n =80), 21 had MCD. Almost all patients diagnosed in adulthood had a kidney biopsy [n = 352 (94%)]; 187 had MCD and 162 had focal segmental glomerulosclerosis. Conclusions: NURTuRE-INS is a prospective cohort study with high-quality biosamples and longitudinal data that will assist research into the mechanistic stratification of INS. Samples and data will be available through a Strategic Access and Oversight Committee.
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Acute poststreptococcal glomerulonephritis is a common cause of acute nephritis in children. Transient hypocomplementemia and complete recovery are typical, with only a minority developing chronic disease. We describe a young girl who developed persistent kidney disease and hypocomplementemia after a streptococcal throat infection. Kidney biopsy 1 year after presentation showed isolated glomerular complement C3 deposition, membranoproliferative changes, and subendothelial, intramembranous and occasional subepithelial electron-dense deposits consistent with C3 glomerulopathy. Complement gene screening revealed a heterozygous single nucleotide insertion in exon 4 of the complement factor H-related protein 5 gene (CFHR5), resulting in a premature stop codon. This variant was not detected in 198 controls. Serum CFHR5 levels were reduced. The mother and sister of the index patient were heterozygous for the sequence variant, with no overt evidence of kidney disease. We speculate that this heterozygous CFHR5 sequence variant is a risk factor for the development of chronic kidney disease after streptococcal infection.
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Proteínas del Sistema Complemento/deficiencia , Proteínas del Sistema Complemento/genética , Glomerulonefritis Membranoproliferativa/genética , Infecciones Estreptocócicas/complicaciones , Niño , Enfermedad Crónica , Complemento C3/análisis , Proteínas del Sistema Complemento/análisis , Femenino , Mutación del Sistema de Lectura , Glomerulonefritis Membranoproliferativa/epidemiología , Glomerulonefritis Membranoproliferativa/etiología , Glomerulonefritis Membranoproliferativa/patología , Heterocigoto , Humanos , Riñón/patología , Linaje , Polimorfismo de Nucleótido Simple , Factores de Riesgo , Análisis de Secuencia de Proteína , Infecciones Estreptocócicas/inmunologíaRESUMEN
IMPORTANCE: In children with corticosteroid-sensitive nephrotic syndrome, many relapses are triggered by upper respiratory tract infections. Four small studies found that administration of daily low-dose prednisolone for 5 to 7 days at the time of an upper respiratory tract infection reduced the risk of relapse, but the generalizability of their findings is limited by location of the studies and selection of study population. OBJECTIVE: To investigate the use of daily low-dose prednisolone for the treatment of upper respiratory tract infection-related relapses. DESIGN, SETTING, AND PARTICIPANTS: This double-blind, placebo-controlled randomized clinical trial (Prednisolone in Nephrotic Syndrome [PREDNOS] 2) evaluated 365 children with relapsing steroid-sensitive nephrotic syndrome with and without background immunosuppressive treatment at 122 pediatric departments in the UK from February 1, 2013, to January 31, 2020. Data from the modified intention-to-treat population were analyzed from July 1, 2020, to December 31, 2020. INTERVENTIONS: At the start of an upper respiratory tract infection, children received 6 days of prednisolone, 15 mg/m2 daily, or matching placebo preparation. Those already taking alternate-day prednisolone rounded their daily dose using trial medication to the equivalent of 15 mg/m2 daily or their alternate-day dose, whichever was greater. MAIN OUTCOMES AND MEASURES: The primary outcome was the incidence of first upper respiratory tract infection-related relapse. Secondary outcomes included overall rate of relapse, changes in background immunosuppressive treatment, cumulative dose of prednisolone, rates of serious adverse events, incidence of corticosteroid adverse effects, and quality of life. RESULTS: The modified intention-to-treat analysis population comprised 271 children (mean [SD] age, 7.6 [3.5] years; 174 [64.2%] male), with 134 in the prednisolone arm and 137 in the placebo arm. The number of patients experiencing an upper respiratory tract infection-related relapse was 56 of 131 (42.7%) in the prednisolone arm and 58 of 131 (44.3%) in the placebo arm (adjusted risk difference, -0.02; 95% CI, -0.14 to 0.10; P = .70). No evidence was found that the treatment effect differed according to background immunosuppressive treatment. No significant differences were found in secondary outcomes between the treatment arms. A post hoc subgroup analysis assessing the primary outcome in 54 children of South Asian ethnicity (risk ratio, 0.66; 95% CI, 0.40-1.10) vs 208 children of other ethnicity (risk ratio, 1.11; 95% CI, 0.81-1.54) found no difference in efficacy of intervention in those of South Asian ethnicity (test for interaction P = .09). CONCLUSIONS AND RELEVANCE: The results of PREDNOS 2 suggest that administering 6 days of daily low-dose prednisolone at the time of an upper respiratory tract infection does not reduce the risk of relapse of nephrotic syndrome in children in the UK. Further work is needed to investigate interethnic differences in treatment response. TRIAL REGISTRATION: isrctn.org Identifier: ISRCTN10900733; EudraCT 2012-003476-39.
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Síndrome Nefrótico , Infecciones del Sistema Respiratorio , Corticoesteroides/uso terapéutico , Niño , Humanos , Masculino , Síndrome Nefrótico/complicaciones , Síndrome Nefrótico/tratamiento farmacológico , Prednisolona/uso terapéutico , Calidad de Vida , Recurrencia , Infecciones del Sistema Respiratorio/tratamiento farmacológico , Infecciones del Sistema Respiratorio/prevención & controlRESUMEN
BACKGROUND: Most children with steroid-sensitive nephrotic syndrome have relapses that are triggered by upper respiratory tract infections. Four small trials, mostly in children already taking maintenance corticosteroid in countries of different upper respiratory tract infection epidemiology, showed that giving daily low-dose prednisone/prednisolone for 5-7 days during an upper respiratory tract infection reduces the risk of relapse. OBJECTIVES: To determine if these findings were replicated in a large UK population of children with relapsing steroid-sensitive nephrotic syndrome on different background medication or none. DESIGN: A randomised double-blind placebo-controlled trial, including a cost-effectiveness analysis. SETTING: A total of 122 UK paediatric departments, of which 91 recruited patients. PARTICIPANTS: A total of 365 children with relapsing steroid-sensitive nephrotic syndrome (mean age 7.6 ± 3.5 years) were randomised (1 : 1) according to a minimisation algorithm based on background treatment. Eighty children completed 12 months of follow-up without an upper respiratory tract infection. Thirty-two children were withdrawn from the trial (14 prior to an upper respiratory tract infection), leaving a modified intention-to-treat analysis population of 271 children (134 and 137 children in the prednisolone and placebo arms, respectively). INTERVENTIONS: At the start of an upper respiratory tract infection, children received 6 days of prednisolone (15 mg/m2) or an equivalent dose of placebo. MAIN OUTCOME MEASURES: The primary outcome was the incidence of first upper respiratory tract infection-related relapse following any upper respiratory tract infection over 12 months. The secondary outcomes were the overall rate of relapse, changes in background treatment, cumulative dose of prednisolone, rates of serious adverse events, incidence of corticosteroid adverse effects, change in Achenbach Child Behaviour Checklist score and quality of life. Analysis was by intention-to-treat principle. The cost-effectiveness analysis used trial data and a decision-analytic model to estimate quality-adjusted life-years and costs at 1 year, which were then extrapolated over 16 years. RESULTS: There were 384 upper respiratory tract infections and 82 upper respiratory tract infection-related relapses in the prednisolone arm, and 407 upper respiratory tract infections and 82 upper respiratory tract infection-related relapses in the placebo arm. The number of patients experiencing an upper respiratory tract infection-related relapse was 56 (42.7%) and 58 (44.3%) in the prednisolone and placebo arms, respectively (adjusted risk difference -0.024, 95% confidence interval -0.14 to 0.09; p = 0.70). There was no evidence that the treatment effect differed when data were analysed according to background treatment. There were no significant differences in secondary outcomes between treatment arms. Giving daily prednisolone at the time of an upper respiratory tract infection was associated with increased quality-adjusted life-years (0.9427 vs. 0.9424) and decreased average costs (£252 vs. £254), when compared with standard care. The cost saving was driven by background therapy and hospitalisations after relapse. The finding was robust to sensitivity analysis. LIMITATIONS: A larger number of children than expected did not have an upper respiratory tract infection and the sample size attrition rate was adjusted accordingly during the trial. CONCLUSIONS: The clinical analysis indicated that giving 6 days of daily low-dose prednisolone at the time of an upper respiratory tract infection does not reduce the risk of relapse of steroid-sensitive nephrotic syndrome in UK children. However, there was an economic benefit from costs associated with background therapy and relapse, and the health-related quality-of-life impact of having a relapse. FUTURE WORK: Further work is needed to investigate the clinical and health economic impact of relapses, interethnic differences in treatment response, the effect of different corticosteroid regimens in treating relapses, and the pathogenesis of individual viral infections and their effect on steroid-sensitive nephrotic syndrome. TRIAL REGISTRATION: Current Controlled Trials ISRCTN10900733 and EudraCT 2012-003476-39. FUNDING: This project was funded by the National Institute for Health Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 26, No. 3. See the NIHR Journals Library website for further project information.
Steroid-sensitive nephrotic syndrome is a kidney condition in which protein leaks into the urine, causing generalised swelling. In most children, the condition recurs or relapses. Relapses often occur following an upper respiratory tract infection (i.e. a cough, cold or sore throat). Research in tropical countries suggests that if children have a small dose of daily steroids for a week at the time of an upper respiratory tract infection then they are less likely to relapse. The selection of children for these studies and the different patterns of infection mean that we are not certain if this treatment would work in the UK. A total of 365 children with relapsing nephrotic syndrome took part. Half of the children took a steroid and the other half took dummy tablets (placebo) for 6 days at the start of an upper respiratory tract infection. We followed up the children for 12 months and collected information on relapses and other treatments and information from questionnaires about behaviour and quality of life. We also investigated whether or not there were cost savings with this treatment. There were 271 children who had an upper respiratory tract infection in the 12 months of the study and so only these children were included in the analyses. Giving 6 days of a low-dose steroid at the time of an upper respiratory tract infection did not reduce the risk of a relapse. There was also no effect on the overall number of relapses, the number of children needing to start extra preventative treatments or side effects of steroids. Although there was no clinical effect, the economic evaluation found that giving prednisolone led to lower treatment costs overall and higher quality of life and might, therefore, offer better value for money, but this has to be interpreted against the clinical evidence of no significant effect. Our conclusion is that there is no clinical benefit to giving children low-dose prednisolone at the time of an upper respiratory tract infection.
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Síndrome Nefrótico , Infecciones del Sistema Respiratorio , Niño , Preescolar , Análisis Costo-Beneficio , Humanos , Recurrencia Local de Neoplasia , Síndrome Nefrótico/tratamiento farmacológico , Prednisolona/efectos adversos , Prednisolona/uso terapéutico , Calidad de Vida , Infecciones del Sistema Respiratorio/tratamiento farmacológico , Infecciones del Sistema Respiratorio/epidemiologíaRESUMEN
BACKGROUND: Childhood steroid-sensitive nephrotic syndrome is a frequently relapsing disease with significant short- and long-term complications, leading to high healthcare costs and reduced quality of life for patients. The majority of relapses are triggered by upper respiratory tract infections (URTIs) and evidence shows that daily low-dose prednisolone at the time of infection may reduce the risk of relapse. OBJECTIVE: The aim of this study was to assess the cost effectiveness of a 6-day course of low-dose prednisolone at the start of a URTI when compared with placebo. METHODS: A state-transition Markov model was developed to conduct a cost-utility analysis with the outcome measured in quality-adjusted life-years (QALYs). Resource use and outcome data were derived from the PREDNOS2 trial. The analysis was performed from a UK National Health Service perspective and the results were extrapolated to adulthood. Model parameter and structural uncertainty were assessed using sensitivity analyses. RESULTS: The base-case results showed that administering low-dose prednisolone at the time of a URTI generated more QALYs and a lower mean cost at 1 year compared with placebo. In the long-term, low-dose prednisolone was associated with a cost saving (£176) and increased effectiveness (0.01 QALYs) compared with placebo and thus remained the dominant treatment option. These findings were robust to all sensitivity analyses. CONCLUSION: A 6-day course of low-dose prednisolone at the time of a URTI in children with steroid-sensitive nephrotic syndrome has the potential to reduce healthcare costs and improve quality of life compared with placebo.
RESUMEN
Genetic testing for pathogenic COL4A3-5 variants is usually undertaken to investigate the cause of persistent hematuria, especially with a family history of hematuria or kidney function impairment. Alport syndrome experts now advocate genetic testing for persistent hematuria, even when a heterozygous pathogenic COL4A3 or COL4A4 is suspected, and cascade testing of their first-degree family members because of their risk of impaired kidney function. The experts recommend too that COL4A3 or COL4A4 heterozygotes do not act as kidney donors. Testing for variants in the COL4A3-COL4A5 genes should also be performed for persistent proteinuria and steroid-resistant nephrotic syndrome due to suspected inherited FSGS and for familial IgA glomerulonephritis and kidney failure of unknown cause.
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Autoantígenos/genética , Colágeno Tipo IV/genética , Pruebas Genéticas/normas , Nefritis Hereditaria/diagnóstico , Nefritis Hereditaria/genética , Nefritis Hereditaria/terapia , Humanos , Guías de Práctica Clínica como AsuntoRESUMEN
The recent Chandos House meeting of the Alport Variant Collaborative extended the indications for screening for pathogenic variants in the COL4A5, COL4A3 and COL4A4 genes beyond the classical Alport phenotype (haematuria, renal failure; family history of haematuria or renal failure) to include persistent proteinuria, steroid-resistant nephrotic syndrome, focal and segmental glomerulosclerosis (FSGS), familial IgA glomerulonephritis and end-stage kidney failure without an obvious cause. The meeting refined the ACMG criteria for variant assessment for the Alport genes (COL4A3-5). It identified 'mutational hotspots' (PM1) in the collagen IV α5, α3 and α4 chains including position 1 Glycine residues in the Gly-X-Y repeats in the intermediate collagenous domains; and Cysteine residues in the carboxy non-collagenous domain (PP3). It considered that 'well-established' functional assays (PS3, BS3) were still mainly research tools but sequencing and minigene assays were commonly used to confirm splicing variants. It was not possible to define the Minor Allele Frequency (MAF) threshold above which variants were considered Benign (BA1, BS1), because of the different modes of inheritances of Alport syndrome, and the occurrence of hypomorphic variants (often Glycine adjacent to a non-collagenous interruption) and local founder effects. Heterozygous COL4A3 and COL4A4 variants were common 'incidental' findings also present in normal reference databases. The recognition and interpretation of hypomorphic variants in the COL4A3-COL4A5 genes remains a challenge.
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Consenso , Pruebas Genéticas/métodos , Nefritis Hereditaria/genética , Guías de Práctica Clínica como Asunto , Autoantígenos/genética , Colágeno Tipo IV/genética , Pruebas Genéticas/normas , Humanos , Nefritis Hereditaria/diagnóstico , FenotipoRESUMEN
Increasing evidence implicates activation of NF-kappaB in a variety of glomerular diseases, but the mechanisms involved are unknown. Here, upregulation of NF-kappaB in the podocytes of transgenic mice resulted in glomerulosclerosis and proteinuria. Absence of the podocyte protein nephrin resulted in NF-kappaB activation, suggesting that nephrin negatively regulates the NF-kappaB pathway. Signal transduction assays supported a functional relationship between nephrin and NF-kappaB and suggested the involvement of atypical protein kinase C (aPKCzeta/lambda/iota) as an intermediary. We propose that disruption of the slit diaphragm leads to activation of NF-kappaB; subsequent upregulation of NF-kappaB-driven genes results in glomerular damage mediated by NF-kappaB-dependent pathways. In summary, nephrin may normally limit NF-kappaB activity in the podocyte, suggesting a mechanism by which it might discourage the evolution of glomerular disease.
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Proteínas Reguladoras de la Apoptosis/metabolismo , Glomerulonefritis/metabolismo , Proteínas de la Membrana/metabolismo , FN-kappa B/metabolismo , Podocitos/metabolismo , Animales , Proteínas Reguladoras de la Apoptosis/genética , Línea Celular , Citoplasma/metabolismo , Perros , Silenciador del Gen , Humanos , Péptidos y Proteínas de Señalización Intracelular/metabolismo , Ratones , Ratones Noqueados , Proteína Quinasa C/metabolismo , Proteinuria/metabolismo , Factor de Transcripción ReIA/metabolismoRESUMEN
BACKGROUND AND OBJECTIVES: Intensified immunosuppression in steroid-resistant nephrotic syndrome is broadly applied, with disparate outcomes. This review of patients from the United Kingdom National Study of Nephrotic Syndrome cohort aimed to improve disease stratification by determining, in comprehensively genetically screened patients with steroid-resistant nephrotic syndrome, if there is an association between response to initial intensified immunosuppression and disease progression and/or post-transplant recurrence. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: Pediatric patients with steroid-resistant nephrotic syndrome were recruited via the UK National Registry of Rare Kidney Diseases. All patients were whole-genome sequenced, whole-exome sequenced, or steroid-resistant nephrotic syndrome gene-panel sequenced. Complete response or partial response within 6 months of starting intensified immunosuppression was ascertained using laboratory data. Response to intensified immunosuppression and outcomes were analyzed according to genetic testing results, pattern of steroid resistance, and first biopsy findings. RESULTS: Of 271 patients, 178 (92 males, median onset age 4.7 years) received intensified immunosuppression with response available. A total of 4% of patients with monogenic disease showed complete response, compared with 25% of genetic-testing-negative patients (P=0.02). None of the former recurred post-transplantation. In genetic-testing-negative patients, 97% with complete response to first intensified immunosuppression did not progress, whereas 44% of nonresponders developed kidney failure with 73% recurrence post-transplant. Secondary steroid resistance had a higher complete response rate than primary/presumed resistance (43% versus 23%; P=0.001). The highest complete response rate in secondary steroid resistance was to rituximab (64%). Biopsy results showed no correlation with intensified immunosuppression response or outcome. CONCLUSIONS: Patients with monogenic steroid-resistant nephrotic syndrome had a poor therapeutic response and no post-transplant recurrence. In genetic-testing-negative patients, there was an association between response to first intensified immunosuppression and long-term outcome. Patients with complete response rarely progressed to kidney failure, whereas nonresponders had poor kidney survival and a high post-transplant recurrence rate. Patients with secondary steroid resistance were more likely to respond, particularly to rituximab.