As family 2 presented here, a positive family history of hematuria and ESRD, diffuse thinning of the GBM observed in the proband’s daughter, and the haplotype of three microsatellite markers around the COL4A5 gene co-segregated with the proband and her affected daughter were important clues in making a diagnosis of XLAS. This evidence concerns the gene COL4A5 and X-linked hydrocephalus with stenosis of the aqueduct of Sylvius.