COL4A5 and Alport syndrome: Estimates of the prevalence of Alport syndrome vary from one in 5,000 to one in 53,000 of the population [1, 2], but the frequent finding of likely pathogenic COL4A5 variants in normal reference datasets and cohorts with renal failure suggests that X-linked disease affects closer to closer to one in 5,000 [3, 4].