ABSTRACT
Resumen: La podocina es una proteína localizada en el diafragma de filtración glomerular donde participa en la regulación de la filtración glomerular. Las mutaciones del gen NPHS2, que codifica a la podocina, son la principal causa de síndrome nefrótico corticorresistente (SNCR) autosómico recesivo en niños. Objetivos: Identificar mutaciones de NPHS2 en niños chilenos con SNCR, y establecer la prevalencia de las variantes más frecuentes en un grupo de adultos sanos. Pacientes y método: Análisis mutacional de NPHS2 en 34 niños chilenos con SNCR. Una vez identificadas las dos variantes de NPHS2 de mayor frecuencia, se realizó un screening de estas mutaciones en 223 adultos sanos. El análisis mutacional se realizó por secuenciación directa de los ocho exones codificantes amplificados por reacción de polimerasa en cadena. La secuenciación del DNA se realizó mediante método fluorométrico y las secuencias fueron evaluadas con el software SeqPilot. La asociación entre la presencia de variantes de NPHS2 y SNCR se calculó comparando las frecuencias alélicas entre los pacientes con SNCR y los voluntarios sanos utilizando prueba exacta de Fisher. Se consideró significativo p < 0,05. Resultados: Se detectaron mutaciones patogénicas de NPHS2 en siete de los 34 pacientes (21%) estudiados, de los cuales seis resultaron heterocigotos para p.R229Q y p.A284 V. En voluntarios sanos la prevalencia de p.R229Q fue de 2,46%. Conclusiones: Este estudio muestra que p.R229Q y p.A284 V son las variantes de NPHS2 más frecuentes en niños chilenos con SNCR. Por primera vez se describe esta asociación en niños chilenos, en base a la cual es posible proponer una estrategia de screening para estudio genético en pacientes con SNCR y sus familias. Se propone una estrategia de búsqueda de p.R229Q y p.A284 V en forma paralela o secuencial en estos pacientes.
Abstract: Podocin is a protein located in the glomerular slit diaphragm where it takes part in the regulation of glomerular filtration. Mutations of the NPHS2 gene that codes podocin are the main cause of autosomal recessive steroid resistant nephrotic syndrome (SRNS). Objectives: To identify the NPHS2 mutations in Chilean children with SRNS, and to determine the prevalence of the most common variants in a group of healthy adults. Patients and methods: Mutation analysis of NPHS2 in 34 Chilean children with SRNS. Once the two most common variants of NPHS2 were identified, screening for these mutations was performed on 233 healthy adults. The mutation analysis was performed by the direct sequencing of the eight coding exons by polymerase chain reaction amplification. The DNA sequencing was performed using a fluorometric method, and then evaluated with SeqPilot™ software. The relationship between the presence of NPHS2 variants and SRNS was calculated by comparing the allele frequency between patients with SRNS and those of the healthy volunteers using the exact Fisher test. A P < .05 was considered significant. Results: Pathogenic NPHS2 mutations were detected in 7 (21%) of the 34 patients studied, of which 6 were heterozygotes for p.R229Q and p.A284 V. The presence of p.R229Q was 2.46% in the healthy volunteers. Conclusions: This study shows that p.R229Q and p.A284 V are the most frequent variants in Chilean children with SRNS. It is the first time that this relationship has been reported in Chilean children. Based on this, a screening strategy is proposed for the genetic study in patients with SRNS and their families. A parallel or sequential search strategy for p.R229Q and p.A284 V in these patients is proposed.
Subject(s)
Humans , Male , Female , Child , Adolescent , Adult , Middle Aged , Aged , Young Adult , Intracellular Signaling Peptides and Proteins/genetics , Membrane Proteins/genetics , Mutation , Nephrotic Syndrome/congenital , DNA Mutational Analysis , Chile , Polymerase Chain Reaction , Exons , Cross-Sectional Studies , Sequence Analysis, DNA , Fluorometry , Gene Frequency , Nephrotic Syndrome/geneticsABSTRACT
Background: Hypovitaminosis D has a high prevalence among patients with chronic kidney disease (CKD). Aim: To determine the prevalence of 25 hydroxy vitamin D (25(OH) D) insufficiency and deficiency in pediatric patients on dialysis and kidney transplantation. Material and Methods: Serum calcium and phosphorus, parathormone (PTH), alkaline phosphatases and 25 (OH)D were measured in 13 children on hemodialysis (HD), 18 on peritoneal dialysis (PD) and 53 that received an allograft (Tx), aged 9.8 ± 4.6 years (51 percent females). Results: Fifty four percent of patients had height Z score less than -1.88. Patients on HD had the lowest values. The average time of replacement therapy was 2.9 ± 2.8 years. Mean 25(OH)D levels in all was 18.7 ± 10.7ng/ml (HD: 21 ± 16.8, PD: 18.9 ± 8.5, Tx: 18.1 ± 9.72 ng/ml). Eighty eight percent of patients had levels below 30 ng/ml. Mean of serum calcium was 9.5 ± 0.64 mg/dl, serum phosphorus 5.03 ± 1.02 mg/dl, calcium-phosphorus product 48 ± 11.8 mg/dl and alkaline phosphatases 300.5 ± 171.3 IU/L. Average PTH values in dialyzed and Tx patients were 724.6 ± 640.5 and 107.7 ± 56.2 pg/ml, respectively (p < 0.001). A positive correlation between 25 (OH) D and calcium levels among PD patients was observed (r = 0.490, p = 0.04). Conclusions: Hypovitaminosis D is highly prevalent among children on renal substitution therapy, regardless of the type of therapy used and the stage of renal failure.