Clinical and pathological investigation of oligomeganephronia

Oligomeganephronia with PAX2 gene deletion diagnosed at the third renal biopsy: a case report

Oligomeganephronia is a congenital anomaly of the kidney and urinary tract. It is often categorized as one of the hypoplastic kidney conditions. The pathological diagnosis of oligomeganephronia is challenged by the absence of clear diagnostic criteria, which often leads to subjective interpretations by pathologists. This report presents the case of a 7-year-old girl who was diagnosed with oligomeganephronia through a third renal biopsy, which was confirmed by gene analysis revealing PAX2 deletion. Two previous renal biopsies, with the naked eye through a microscope, failed to identify glomerular hypertrophy and sparse glomerular distribution density. However, using digital images, the glomeruli were larger than those of age-matched controls, and the number of glomeruli within the renal cortex area revealed sparse glomerular distribution density. Image processing allows for objective evaluation of the glomerular size and glomerular distribution density, providing a quantitative assessment. For earlier diagnosis of oligomeganephronia, an appropriate objective standardized method for measuring glomerular size and glomerular distribution density should be established.

A novel pathogenic variant c.262delA in PBX1 causing oligomeganephronia identified using whole-exome sequencing and a literature review

Oligomeganephronia (OMN) is a rare congenital renal hypoplasia reported more often in children than in adults. The diagnosis of OMN relies on renal biopsy and exhibits a significant reduction in the number of glomeruli and pronounced glomerular hypertrophy. Here, we report the case of an 8-year-old boy with recurrent proteinuria and abnormal external ears. A renal biopsy revealed large and rare glomeruli. The histological findings confirmed the diagnosis of OMN. Whole-exome sequencing of the patient revealed a new pathogenic variant in PBX1 (hg19, NM_002585, c.262delA, p.Thr88Glnfs*3). The PBX1 gene encodes a transcription factor whose pathogenic variants can result in congenital renal and urinary system anomalies, with or without hearing loss, abnormal ears, and developmental retardation (CAKUTED). This is the first report to detect PBX1 pathogenic variants in children with OMN, a novel phenotype of human PBX1 pathogenic variants. We performed functional prediction analyses of deletions in the corresponding structural domains. We summarized 27 cases of PBX1 single pathogenic variants reported between 2003 and 2023 in terms of truncating and missense pathogenic variants, which can deepen our understanding of the PBX1 structural domain and expand our knowledge of the PBX1 genotype and phenotype.