A unique evolution of the kidney phenotype in a patient with autosomal recessive Alport syndrome.

Alport syndrome is due to mutations in one of the genes encoding (α3,4,5) type IV collagen resulting in defective type IV collagen, a key component of the glomerular basement membrane (GBM). The GBM is initially thin and, with ongoing remodeling, develops a thickened basket-woven appearance. We report a unique case of a 9-year-old boy who underwent biopsy for hematuria and proteinuria, diagnosed as IgA nephropathy, with normal GBM appearance and thickness. Because of a family history of hematuria and chronic kidney disease, he subsequently underwent genetic evaluation, and a mutation of α3 type IV collagen (COL4A3) was detected. Additional studies of the initial biopsy demonstrated abnormal type IV collagen immunostaining. A repeat biopsy 4 years later showed characteristic glomerular basement membrane morphology of Alport syndrome and scarring consistent with sequelae of IgA nephropathy. This is the first description of this unusual transition from an initial normal appearance of the glomerular basement membrane to the classic Alport phenotype.