Does Zika virus infection induce prolonged remissions in children with idiopathic nephrotic syndrome?

BACKGROUND: Zika is an emerging mosquito-borne flavivirus. We report two pediatric patients diagnosed with idiopathic nephrotic syndrome who achieved complete remission of the disease after suffering Zika virus (ZIKV) infection. CASE DIAGNOSIS/TREATMENT: The first patient was a young girl aged 2.5 years with steroid-dependent nephrotic syndrome who was subsequently diagnosed with ZIKV infection. Following the infection, the steroid dose could be reduced until complete withdrawal. The patient persists in complete remission. The second patient was a steroid-resistant boy aged 7 years who was scheduled for a renal biopsy when he was diagnosed with ZIKV infection. A week after the recovery phase of the acute rash, proteinuria was noted to be gradually falling. Today, 12 months later, he is in complete remission of the disease. CONCLUSIONS: We are aware that the improvement observed in our two patients after ZIKV infection may be be random. However, it is also possible that future studies will discover that ZIKV infection has some effect on the cellular immune system similar to that of measles infection.

Distal Renal Tubular Acidosis Screening by Urinary Acidification Testing in Mexican Children.

BACKGROUND: Primary distal renal tubular acidosis is a clinical disorder characterized by hyperchloremic metabolic acidosis, hypercalciuria, hypocitraturia, urinary acidification impairment, hypokalemia, metabolic bone disease, and nephrocalcinosis. Urinary acidification ability may be evaluated by an acidification test or maximum urinary pCO2 assessment with alkaline urine. The maximum urinary pCO2 test using acetazolamide and sodium bicarbonate is an easy test to confirm the lack of urine acidification in distal renal tubular acidosis in children. OBJECTIVE: To determine the urinary acidification ability using the maximum urinary pCO2 assessment in a group of children with a distal renal tubular acidosis diagnosis. MATERIAL AND METHODS: Thirty children were evaluated (13 males and 17 females); 23 children had been diagnosed with distal renal tubular acidosis by other physicians and were under alkali treatment with potassium and sodium citrates (21) and bicarbonate (2), and five children were not under alkali treatment. Two children had been diagnosed with primary distal renal tubular acidosis by our medical group. The maximum urinary pCO2 was determined by the oral intake of acetazolamide and sodium bicarbonate. RESULTS: Two cases with primary distal renal tubular acidosis were found, and they had a history of dehydration episodes during infancy and showed hyperchloremic metabolic acidosis with hypokalemia. They also exhibited urine acidification impairment with furosemide and reduced urinary pCO2 (< 60 mmHg), and the urine-blood pCO2 gradient was reduced in both cases (< 30 mmHg). One of them developed bilateral sensorineural deafness, while the other showed severe hypocitraturia. One case of proximal or type 2 renal tubular acidosis with hyperaminoaciduria was identified. Twenty-eight children displayed normal urinary acidification and did not show signs of distal renal tubular acidosis. CONCLUSIONS: The urinary acidification test with furosemide and urinary pCO2 assessment are reliable tests to identify the renal excretion of hydrogen ions (H+) and allow confirmation of the lack of urine acidification in distal renal tubular acidosis.

Mutación G47R en el gen SBSN causa síndrome de Bartter con sordera en dos hermanas venezolanas / Bartter syndrome with deafness in two venezuelan sisters

El Síndrome de Bartter (SB) es un grupo heterogéneo de tubulopatías autosómicas recesivas, perdedoras de sal e hipokalémicas. Se han identificado cinco tipos de SB causados por diferentes defectos genéticos, uno de ellos está asociado con sordera neurosensorial (SBSN). Recientemente se han descrito mutaciones en el gen SBND, mapeado en el cromosoma 1p31, asociadas con BSNS. El gen Barttin, codifica para una subunidad B esencial, subunidad de los canales ClC-ka y ClC-kb. Ambas subunidades están co- expresadas en la membrana basolateral de los túbulos renales, en las ramas delgada y gruesa del asa de Henle, y en la vascularización del oído interno. En el presente trabajo se describen los casos clínicos de dos hermanas venezolanas hijas de padres consanguíneos (primo-hermanos) de Jadacaquiva en la Península de Paraguaná, estado Falcón. La secuencia de análisis del gen SBSN mostró que las niñas afectadas eran homocigotas para una transición C-T en axón 1. Esta alteración resulta en una mutación ausente, G47R, la cual suprime el efecto estimulante sobre el barttin de la subunidad del canal ClC-KB. Estas niñas con la mutación G47R presentaron polihidramnios, partoprematuro y pérdida de sal. Sin embargo, la tasa de filtración glomerular de las pacientes es normal. Las manifestaciones clínicas son más moderadas en pacientes con mutación G47R, en relación a otros pacientes publicados con SBSN. Éste es el primer reporte de casos con SBSN en Venezuela.

Bartter syndrome (BS) is a heterogeneous group of autosomal recessive hypokalemic salt-losing tubulopathies. Five types of BS caused by different genetic defects have been identified, and one of them is associated with sensorineural deafness (BSND). Mutations in the recently described BSND gene, mapped in chromosome 1p31, have been reported to be associated with BSNS. This gene encodes barttin, an essential B-subunit ClC-ka and ClC-kb channels. Both subunits are co-expressed in basolateral membranes of renal tubules in the thin and thick ascending limb of Henle’s loop and in the stria vascularis of the inner ear. We studied two venezuelan sisters, daughters of consanguineous parents from a small town called Jadacaquiva, in the peninsula of Paraguaná, Venezuela. Sequence analysis of the BSND gene showed that the affected members were homozygous for C to T transition in axon 1. This alteration results in a missense mutation, G47R that has been previously shown to abolish the stimulatory effect on the subunit barttin of the ClC-Kb channel. The patients with the G47R mutation presented polyhidramnios, premature birth and salt loss. Nevertheless, glomerular filtration rate is normal. Clinical manifestations are moderate in patients with G47R mutation with regard to other patients reported with BSND. This is the first report of BSND in Venezuela.

Válvulas de uretra posterior y ausencia de reflujo vesicoureteral bilateral: Seguimiento de la función renal / Posterior urethral valves and lack of bilateral vesicoureteral reflux: Renal function follow-up background

Introducción. Las válvulas de uretra posterior congénitas son repliegues de mucosa que se originan únicamente en varones. Constituyen la causa más común de obstrucción de la vía urinaria en el período neonatal. Debido a la alta presión que se genera en la vejiga urinaria, con frecuencia se acompañan de reflujo vesicoureteral (RVU) bilateral. En ocasiones, el reflujo es unilateral, asociado a displasia renal homolateral (síndrome VURD). Se ha comunicado que en estos casos el pronóstico a largo plazo es mejor, no obstante, existe muy poca experiencia sobre éste en el subtipo constituido por los niños en los que no existe reflujo. Métodos. Se estudiaron a 4 pacientes con válvulas de uretra posterior y ausencia de RVU, en seguimiento por un tiempo comprendido entre 3 y 6 años. Se describe su evolución desde el diagnóstico, la cirugía realizada, los marcadores de función renal, estudios de imagen y evolución. Así como los valores de los cocientes calculados entre las concentraciones urinarias de N-acetil-glucosaminidasa (NAG) y de microalbúmina con respecto a la creatinina urinaria. Resultados. La función glomerular renal fue normal en los 4 casos. Únicamente un paciente tenía un discreto defecto de la capacidad de concentración y un ligero incremento en la eliminación urinaria de NAG. Conclusiones. El manejo médico y quirúrgico de las válvulas de uretra posterior ha mejorado la supervivencia de los niños con este diagnóstico. La ausencia de RVU, la presencia de ascitis urinaria o urinoma en el período neonatal y la asociación con un gran divertículo vesical proveen un mecanismo de "escape", lo que resulta en una preservación de la función renal.

Introduction. The posterior urethral congenital valves are mucosal folds in the posterior urethra that occur only in male patients. They are the most common cause of urinary tract obstruction in the neonatal period. Due to hyper pressure that begins in the urinary bladder, it is highly frequent for these to come together with bilateral vesico-ureteral reflux. In some cases, this reflux is unilateral and is associated with posterior urethral valve and renal dysplasia (VURD syndrome). A better long-term renal outcome in these cases has been reported. Nevertheless, there is very little experience regarding prognosis of the remaining group of children without reflux. Methods. We studied 4 children with posterior urethral valves and lack of vesico-ureteral reflux with controlled follow-up during 3 and 6 years. We described disease presentation and clinical course from diagnosis, surgical intervention, renal function, radiologic features, N-acetylglucosaminidase (NAG), and microalbuminuria during follow-up. Results. Renal glomerular function is normal in all 4 cases. Only one patient had a mild default in urinary concentration capacity and a slight increase in urinary elimination of N-acetylglucosaminidase. Conclusion. Medical and surgical management of the posterior urethral valves has improved long-term renal outcome in the sepatients. Lack of vesico-ureteral reflux, urinary ascites, urinary extravasation, and large congenital bladder diverticula can serve as a pop-off mechanism to buffer hyperpressure in the urinary tract, leading to the preservation of improved renal function in boys with posterior urethral valves.