COL4A3, COL4A4, and COL4A5 mutations cause dysfunctional glomerular basement membrane (GBM) in Alport syndrome.10,11 Kidney biopsy specimens from a patient with Alport syndrome, a patient without Alport syndrome, and a patient with a thin membrane lesion demonstrate that the GBM in patients with Alport syndrome is abnormally split and laminated compared with the GBM of patients with other conditions. In patients with a thin basement membrane lesion, which is now proposed to be considered as Alport syndrome, the GBM is abnormally thin. Images used with permission from UNC Kidney Center. www.unckidneycenter.org. Accessed April 20, 2020.