A Case of Autosomal Dominant Alport Syndrome with Normal Type IV Collagen α5 Staining Diagnosed by a Genetic Analysis.

A 30-year-old woman with persistent hematuria, mild proteinuria, and a family history of end-stage kidney disease was initially diagnosed with thin basement membrane nephropathy based on renal biopsy findings of a nearly normal glomerular basement membrane with only focal thinning, no lamellation, and normal type IV collagen α5 staining. However, genetic testing identified a heterozygous COL4A4 missense variant (p.Gly527Cys), thus confirming a diagnosis of autosomal dominant Alport syndrome. After starting angiotensin receptor blocker therapy, the patient's kidney function remained stable. This case highlights the importance of genetic testing in accurately distinguishing autosomal dominant Alport syndrome from thin basement membrane nephropathy when the biopsy findings are inconclusive.