Background There is little information about Coronavirus Disease 2019 (COVID-19) in children with underlying chronic renal pathologies. Cases report From March until April 15, 2020, 16 children with chronic renal pathologies were diagnosed with COVID-19 in Spain. Of these, 6 had end-stage kidney disease (ESKD) (3 transplant recipients and 3 on chronic hemodialysis). The severity of symptoms was mild in all the patients, with little radiological involvement. Three patients were asymptomatic. Fever and upper respiratory symptoms were the most frequent findings. Basal glomerular filtration worsened in 3 patients; however, recovery was rapidly achieved with rehydration and drug dose adjustment. In 2 patients diagnosed with steroid-dependent nephrotic syndrome, COVID-19 provoked a disease relapse. None required oxygen therapy, and 7 could be managed as outpatients. Conclusions COVID-19 disease appears to have a similar clinical course in children with underlying chronic renal pathologies, even in immunosuppressed cases, as in healthy children of the same age; however, special attention must be paid to fluid management and drug dose adjustment.

Key Points: Kidney survival in C3 glomerulopathy is significantly higher in patients with a disease chronicity score <4 and proteinuria <3.5 g/d, regardless of baseline eGFR. A faster eGFR decline in C3 glomerulopathy is associated with higher probability of kidney failure. Patients with glomerulopathy with a progressive reduction in proteinuria over time did not reach kidney failure. Background: C3 glomerulopathy is a rare kidney disease, which makes it difficult to collect large cohorts of patients to better understand its variability. The aims of this study were to describe the clinical profiles and patterns of progression of kidney disease. Methods: This was a retrospective, observational cohort study. Patients diagnosed with C3 glomerulopathy between 1995 and 2020 were enrolled. Study population was divided into clinical profiles by combining the following predictors: eGFR under/above 30 ml/min per 1.73 m², proteinuria under/above 3.5 g/d, and histologic chronicity score under/above 4. The change in eGFR and proteinuria over time was evaluated in a subgroup with consecutive measurements of eGFR and proteinuria. Results: One hundred and fifteen patients with a median age of 30 years (interquartile range 19–50) were included. Patients were divided into eight clinical profiles. Kidney survival was significantly higher in patients with a chronicity score <4 and proteinuria <3.5 g/d, both in those presenting with an eGFR under/above 30 ml/min per 1.73 m². The median eGFR slope of patients who reached kidney failure was −6.5 ml/min per 1.73 m² per year (interquartile range −1.6 to −17). Patients who showed a reduction in proteinuria over time did not reach kidney failure. On the basis of the rate of eGFR decline, patients were classified as faster eGFR decline (≥5 ml/min per 1.73 m² per year), slower (<5 ml/min per 1.73 m² per year), and those without decline. A faster eGFR decline was associated with higher probability of kidney failure. Conclusions: Kidney survival is significantly higher in patients with a chronicity score <4 and proteinuria <3.5 g/d regardless of baseline eGFR, and a faster rate of decline in eGFR is associated with higher probability of kidney failure.

The complement system is a network of soluble and cell surface proteins primarily involved in innate immune responses. Complement signaling is essential for pathogen defence and homeostasis, but an activation-regulation imbalance can lead to tissue damage. This phenomenon has been implicated in kidney diseases such as atypical Haemolytic Uraemic Syndrome (aHUS), frequently associated with dysfunction of the complement regulator Factor H (FH). Physiologically, complement interacts with the coagulation, fibrinolysis, renin-angiotensin and kallikrein-kinin systems (KKS). The KKS is a proinflammatory and procoagulant cascade comprised of the protease prekallikrein, the coagulation factors XI (FXI) and XII (FXII), and the cofactor/substrate high-molecular-weight kininogen. KKS can be activated conformationally or proteolytically. KKS activation in vitro triggers a number of biochemical interactions between FXI, FXII, FH and other complement proteins that result in direct or secondary complement activation. These functional links point to an overall complement pro-activating role for the KKS that has implications for coagulation and immunity, but whose physiological consequences in vivo remain largely unexplored. This review aims to summarize the main physiopathological events of KKS activation in the context of complement-mediated kidney disease, with particular emphasis in aHUS.

Contexto: el síndrome nefrótico idiopático (SNI) es la glomerulopatía más frecuente en pediatría y su pronóstico depende fundamentalmente de la respuesta a corticosteroides. Objetivo: el objetivo del estudio fue analizar descriptivamente a pacientes con SNI, buscando parámetros predictivos de la evolución. Metodología: se analizaron retrospectivamente 77 pacientes menores de 16 años (69,6?% varones, mediana de edad de 3,83 años) diagnosticados con SNI entre 2010 y 2022, clasificándolos en síndrome nefrótico corticosensibles (SNCS) y síndrome nefrótico corticorresistentes (SNCR). Resultados: en el grupo de SNCS (65 pacientes), la mediana para la remisión inicial fue de 11,5 días, con media de siete recaídas. El 85,7?% recibió tratamientos alternativos a corticosteroides, siendo el levamisol el más común. Tras 9,9 años de seguimiento, ningún paciente desarrolló enfermedad renal crónica y el 42,8?% estaba en remisión sin tratamiento. Pacientes que necesitaron más de dos fármacos adicionales tenían más edad al diagnóstico y aquellos con respuesta más lenta en el primer brote tendieron a tener más de cuatro recaídas. En el grupo SNCR (12 pacientes), la ciclosporina fue el tratamiento más común. En la mayoría se realizó biopsia, revelando glomeruloesclerosis focal y segmentaria en el 58,3?% de los casos y enfermedad de cambios mínimos (ECM) en el 25?%. Se identificaron mutaciones genéticas en un 50?% de los pacientes, y el 41,6?% necesitaron tratamiento renal sustitutivo (TRS) tras 22 meses desde el diagnóstico. Los pacientes con ECM tuvieron un mejor pronóstico. Conclusiones: una edad mayor al diagnóstico y una respuesta inicial más lenta se asoció con una peor evolución en SNCS. El levamisol fue efectivo como monoterapia en el 28,5?% de los pacientes con SNCS; mientras que un 41?% de pacientes con SNCR requirió TRS a los 22 meses de diagnóstico, siendo el pronóstico más favorable para aquellos con ECM.