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Background: Focal segmental glomerulosclerosis (FSGS) is a histological pattern of glomerular damage that includes idiopathic conditions as well as genetic and non-genetic forms. Among these various etiologies, different phenotypes within the spectrum of congenital anomalies of the kidney and urinary tract (CAKUT) have been associated with FSGS. Summary: Until recently, the main pathomechanism of how congenital kidney and urinary tract defects lead to FSGS was attributed to a reduced number of nephrons, resulting in biomechanical stress on the remaining glomeruli, detachment of podocytes and subsequent inability to maintain normal glomerular architecture. The discovery of deleterious single nucleotide variants in PAX2, a transcription factor crucial in normal kidney development and a known cause of papillorenal syndrome, in individuals with adult-onset FSGS without congenital kidney defects has shed new light on developmental defects that become evident during podocyte injury. Key message: In this mini-review, we challenge the assumption that FSGS in CAKUT is caused by glomerular hyperfiltration alone and hypothesize a multifactorial pathogenesis that includes overlapping cellular mechanisms that are activated in both damaged podocytes as well as nephron progenitor cells.

Background: Focal segmental glomerulosclerosis (FSGS) is a histological pattern of glomerular damage that includes idiopathic conditions as well as genetic and non-genetic forms. Among these various etiologies, different phenotypes within the spectrum of congenital anomalies of the kidney and urinary tract (CAKUT) have been associated with FSGS., Summary: Until recently, the main pathomechanism of how congenital kidney and urinary tract defects lead to FSGS was attributed to a reduced number of nephrons, resulting in biomechanical stress on the remaining glomeruli, detachment of podocytes, and subsequent inability to maintain normal glomerular architecture. The discovery of deleterious single-nucleotide variants in PAX2 , a transcription factor crucial in normal kidney development and a known cause of papillorenal syndrome, in individuals with adult-onset FSGS without congenital kidney defects has shed new light on developmental defects that become evident during podocyte injury., Key Message: In this mini-review, we challenge the assumption that FSGS in CAKUT is caused by glomerular hyperfiltration alone and hypothesize a multifactorial pathogenesis that includes overlapping cellular mechanisms that are activated in both damaged podocytes as well as nephron progenitor cells., Competing Interests: R.W. is supported by a consortium grant from the Dutch Kidney Foundation (20OC002). R.W. is a board member of the working group on CAKUT, urinary tract infection, and bladder dysfunction of the European Society of Pediatric Nephrology (ESPN). E.L. is supported by the ERC Consolidator grant 101045467 – NEOGRAFT. E.L. is a board member of the working group on inherited kidney disorders of the ESPN. R.W. and E.L. are members of the NL research consortium Kidnie, which is supported by the Dutch Kidney Foundation. R.W. and E.L. are working in the reference center of the European Reference Kidney Network (ERKNet)., (© 2024 The Author(s). Published by S. Karger AG, Basel.)