Percutaneous kidney biopsy and the histopathologic patterns of kidney diseases in children: An observational descriptive study at a South-East Nigerian tertiary hospital

Controversy between biopsy and risk in children with proteinuria: is there a paradigm war?

BACKGROUND

Proteinuria is a prevalent symptom of pediatric nephrology, while kidney biopsy remains the gold standard for kidney tissue analysis, and it is currently controversial. We report the rare case that the mutation in the AMN gene was considered to cause chronically isolated proteinuria and also suggest that renal biopsy should be chosen with caution in children with chronic isolated non-nephrotic levels of proteinuria and that genetic testing may be feasible for the early precise diagnosis.

CASE PRESENTATION

A 35-month-old boy presented with excessive urine foaming for more than half a month; his proteinuria was considered non-nephrotic range and urine protein electrophoresis was suggestive of mixed proteinuria; other than that, the investigations are non-specific. Given the child's chronic isolated proteinuria and good renal function, we chose to refine the genetic test rather than a renal biopsy; a compound heterozygous variant was found in the AMN gene of this child which was caused by a point mutation in the father, and a partial chromosomal deletion in the mother.

CONCLUSIONS

Cubilin(encoded by CUBN), amnionless(encoded by AMN), and megalin form a multiligand receptor complex; CUBN or AMN gene variants have been implicated as a hereditary cause of megaloblastic anemia, proteinuria, and neurological impairment. In the past few decades, chronic isolated proteinuria caused by CUBN gene variants is benign, non-progressive, and has normal renal function. However, the child is the first reported case of isolated proteinuria of AMN gene mutation, indicating that the earlier diagnostic genetic sequencing in an otherwise well, not nephrotic proteinuria child may be a convenient, cost-effective, and harmless option, challenging the traditional paradigm.

Implementation of Kidney Biopsy in One of the Poorest Countries in the World: Experience from Zinder Hospital (Niger)

Kidney biopsy (KB) has become essential in the nephrologist's approach to kidney diseases, both for diagnosis, treatment, and prognosis. Our objective is to describe the preliminary results of KBs in Niger, one of the poorest countries in the world. This is a descriptive cross-sectional study that took place over 36 months in the nephrology/dialysis department of the Zinder National Hospital. Biopsy results were obtained in less than 5 working days. Patients were responsible for covering the cost of the kidney biopsy. The data collected were analyzed using Epi Info V7 software. We performed 120 kidney biopsies during the study period. The average age of the patients was 35 years ± 15.4 [5-68]. The male/female sex ratio was 2:1. Patients' medical history included herbal medicine use in 33% of cases and high blood pressure in 27.5% of cases. Proteinuria was present at a rate of ≥3 g/24 h in 46.6% of them. The primary indication for kidney biopsy was glomerular syndrome in 62.5% of cases, including 50% with nephrotic syndrome. All kidney biopsies were performed with real-time ultrasound guidance, using an automatic gun fitted with a 16G needle. Regarding complications, macroscopic hematuria was present in 12.5% of cases. Inadequate kidney biopsy was infrequent (5.8% of cases). The most common findings were (i) glomerular diseases (58.4%), such as membranoproliferative glomerulonephritis (13.3%), focal-segmental glomerulosclerosis (10.6%), lupus nephritis (8.8%), minimal change disease (8%), and membranous nephropathy (2.7%), and (ii) tubulointerstitial changes (31.8%). Diabetic nephropathy was rare (2.6%), as was IgA nephropathy (0.9%). We have demonstrated that implementing a sustainable kidney biopsy program in a very poor country is feasible, thanks to the dedication of a specialized renal pathologist. Having a clear diagnosis can assist in properly treating these renal patients according to international guidelines, thereby delaying the progression to end-stage kidney disease.