Podocyte Biology in Pediatric Glomerular Disease: From Slit Diaphragm Assembly to Genotype-Guided Therapy—A Narrative Review

The podocyte is a terminally differentiated cell whose foot processes and slit diaphragm form the final layer of the glomerular filtration barrier. Because podocytes are not effectively replaced after birth, and nephron number is fixed before it, their cumulative loss converts congenital and steroid-resistant nephrotic syndrome, focal segmental glomerulosclerosis and Alport syndrome into a shared trajectory towards chronic kidney disease. This narrative review, based on a structured search of three databases with the cited evidence classified as pediatric, adult, mixed or preclinical, connects podocyte biology with pediatric nephrology. We follow maturation and the modules whose disruption produces disease, a genetic architecture in which diagnostic yield falls steeply with age at onset, and the convergence of genetic, mechanical, metabolic and immune insults on podocyte depletion. Single-cell and spatial atlases, organoids, glomerulus-on-a-chip systems and human tissue are compared as partly discordant platforms. A molecular result currently changes a small, defined set of clinical decisions. No podocyte-derived urinary marker has been shown in children to add information beyond proteinuria and filtration rate, anti-nephrin antibody assays are not yet standardized, and kidney biopsy remains the reference standard. We set out an integrated diagnostic pathway, state the limitations of the evidence and define research priorities.