Corrigendum: Case report: Unveiling a less severe congenital nephrotic syndrome in a Rapa Nui patient with a NPHS1 Maori founder variant.

[This corrects the article DOI: 10.3389/fneph.2024.1379061.].

Case report: Unveiling a less severe congenital nephrotic syndrome in a Rapa Nui patient with a NPHS1 Maori founder variant.

Background: Congenital nephrotic syndrome (CNS) is a severe kidney disorder characterized by edema, massive proteinuria, and hypoalbuminemia that manifests in utero or within three months after birth. CNS affects 1-3 per 100,000 children, primarily associated with genetic variants and occasionally with infections. Genetic analysis is the first-line method for diagnosis. The most common founder variants have been identified in European populations, often resulting in end-stage kidney disease by 1-2 years of age. Case-diagnosis/treatment: A female full-term neonate, without prenatal signs of kidney disease, was admitted to Rapa Nui (Eastern Island) Hospital at the age of 2 months due to bronchial obstruction. She presented fever, oliguria, edema, urine protein-to-creatinine ratio (UPCR) 433.33, and hypoalbuminemia (0.9 g/dL). She was transferred to a mainland Chilean hospital following CNS diagnosis. Viral screening detected cytomegalovirus (CMV) positivity in both blood and urine. A kidney biopsy revealed interstitial nephritis and diffuse podocyte damage and the tissue PCR resulted negative for CMV. Interviews with the parents revealed consanguinity, suggestive of hereditary CNS. Genetic analysis identified the Maori founder variant, NPHS1 c.2131C>A (p.R711S), in homozygosis. The patient received albumin infusions and antiviral therapy, being discharged when she was 5 months old, with improved laboratory parameters evidenced by UPCR 28.55, albumin 2.5 g/dL, and cholesterol 190 mg/dL. Subsequent clinical monitoring was conducted through virtual and in-person consultations. At her last follow-up at 4 years 2 months old, she presented UPCR 16.1, albumin 3.3 g/dl and cholesterol 220 mg/dL, maintaining normal kidney function and adequate growth. Conclusions: To our knowledge, this represents the first case of CNS in Chile carrying a NPHS1 variant associated with prolonged kidney survival. As described in the Maori population, the patient exhibited a less severe clinical course compared to classical NPHS1 patients. Genetic testing for the Maori founder variant in CNS patients related to the New Zealand population, could impact management decisions and potentially prevent the need for nephrectomies.

Síndromes nefróticos congénitos y hereditarios / Congenital and heritable nephrotic syndromes

En los últimos años se han identificado muchos síndromes nefróticos familiares y esporádicos que no responden a los tratamientos habituales (esteroides e inmunosupresores), evolucionan con relativa rapidez a la insuficiencia renal crónica y se producen por mutaciones genéticas. La mayoría de los síndromes nefróticos que se trasmiten genéticamente y que pueden ser congénitos, presentarse en el primer año de la vida, o en el niño mayor, son atribuidos a mutaciones en los genes NPHS1, NPHS2, WT1 y LAMB2. Otros síndromes nefróticos producidos por mutaciones genéticas pueden no manifestarse hasta la adultez. El objetivo fundamental de esta revisión fue llamar la atención sobre los síndromes nefróticos producidos por mutaciones genéticas en los que no sólo no se obtienen resultados con los tratamientos inmunosupresores, si no en los que dichos tratamientos pueden ser perjudiciales para el paciente

In past years many familial and sporadic nephrotic syndromes refractory to usual treatments (steroids and immunosuppressives), evolve quickly to a chronic renal failure produced by genetic mutations. Most of nephrotic syndromes genetically transmitted and that may be congenital, present in the first year of life or in the older child, are attributable to NPHS1, NPHS2, WT1 and KLAMB2 gen mutations. Other nephrotic syndromes produced by genetic mutations may not appear until adulthood. The main objective of present review was to alert on the nephrotic syndromes produced by genetic mutations without response to immunosuppressive treatments, but on those in which such treatment may be dangerous for patient

El síndrome nefrótico y el diagnóstico genético en pediatría / Inheritance genetics of nephrotic syndrome

Steroid-Resistant Nephrotic Syndrome (SRNS) is found in approximately 20 percent of patients with Nephrotic Syndrome (NS). Podocyte-gen mutations are diagnosed in a half of these children. Nephrin (NPHS1), podocin (NPHS2) and Wilms tumor suppressor gene (WT1) are the most frequently founded mutations. These patients usually progress to End Stage Renal Disease (ESRD). Objective: Current concepts in genetic diagnostic of NS in pediatrics are presented. A local experience is analyzed. In Chilean pediatric patients with SRNS, a mutational analysis of the NPHSl and NPHS2 gene was carried out by direct sequencing of the coding regions following polymerase chain reaction (PCR) amplification of genomic leukocyte DNA with flanking intronic primers. For WTl (exon 8 and exon 9), PCR of these fragments were done. Thirty-three patients were included, 17 males, 11,1 +/- 6.8 years. 54 percent of them developed ESRD, 12 patients were transplanted at the time of the analysis, 5 were under dialysis therapy, and 16 children correspond to ESRD Stage 3 and 4. Genetic analysis showed a gen mutation in 9 patients, NPHSl in 3 and NPHS2 in 6 of them. All genetic NS patients were cyclosporine-resistant. Post transplant relapse of NS was lower in genetic patients (p < 0.05). Conclusion: SRNS in children should be always evaluated from a genetic approach in order to avoid long-term immunosuppression, and to anticipate a clinical evolution after kidney transplantation.

En pediatría, el 20 por ciento de los pacientes portadores de Síndrome Nefrótico Idiopático son corticoresistentes (SNCR). Aproximadamente la mitad de ellos corresponden a mutaciones de genes que codifican proteínas del podocito. Las mutaciones más frecuentes corresponden al gen de la nefrina (NPHS1), la podocina (NPHS2) y del gen supresor del tumos de Wilms (WT1). Estas formas hereditarias no responden a tratamientos inmu-nosupresores y pueden progresar a enfermedad renal terminal (ERT). Objetivo: Revisar el estado actual del diagnóstico genético en Síndrome Nefrótico en niños, y presentar esta experiencia nacional de esta patología. Para el estudio de pacientes pediátricos chilenos, se realizó análisis de mutación del gen NPH2 por secuen-ciación directa de la regiones codificantes por PCR para la amplificación del DNA genómico leucocitario con partidores de acompañamiento intrónico. Para nefrina se procedió a extraer el DNA genómico, y se realizó la búsqueda de mutaciones de NPHSl por secuenciación directa de los 29 exones codificantes y las uniones intrónicas adyacentes, mientras que para el estudio de WTl se practicó el análisis mutacional de los exones 8 y 9, realizado por secuenciación directa del producto amplificado de WT1-PCR. Se han estudiado 33 pacientes provenientes de 29 familias, 17 varones, edad 11,1 +6,8 años. Dieciocho pacientes (54 por ciento) evolucionaron a ERT. Doce pacientes estaban trasplantados, 5 en diálisis, y 16 estaban en etapas 3-4 de enfermedad renal crónica. El estudio genético identificó mutaciones en 9 pacientes (27 por ciento), 3 correspondieron a NPHS1, 6 a NPHS2. Ningún caso con mutación respondió a tratamiento de Ciclosporina A (CsA), y las recaídas posttrasplante fueron significativamente menores en el grupo con mutación (+). Conclusión: Las mutaciones en estos genes deben ser estudiadas en cada niño con SNCR con el fin de evitar tratamientos prolongados e inefectivos, y anticipar la evolución después del trasplante renal.

Analysis of the intronic single nucleotide polymorphism rs#466452 of the nephrin gene in patients with diabetic nephropathy

We present the analysis of an intronic polymorphism of the nephrin gene and its relationship to the development of diabetic nephropathy in a study of diabetes type 1 and type 2 patients. The frequency of the single nucleotide polymorphism rs#466452 in the nephrin gene was determined in 231 patients and control subjects. The C/T status of the polymorphism was assessed using restriction enzyme digestions and the nephrin transcript from a kidney biopsy was examined. Association between the polymorphism and clinical parameters was evaluated using multivaríate correspondence analysis. A bioinformatics analysis of the single nucleotide polymorphism rs#466452 suggested the appearance of a splicing enhancer sequence in intron 24 of the nephrin gene and a modification of proteins that bind to this sequence. However, no change in the splicing of a nephrin transcript from a renal biopsy was found. No association was found between the polymorphism and diabetes or degree of renal damage in diabetes type 1 or 2 patients. The single nucleotide polymorphism rs#466452 of the nephrin gene seems to be neutral in relation to diabetes and the development of diabetic nephropathy, and does not affect the splicing of a nephrin transcript, in spite of a splicing enhancer site.