COL4A5 and X-linked hydrocephalus with stenosis of the aqueduct of Sylvius: Age at ESRD is strongly correlated with COL4A5 genotype in males with XLAS [1–3]; risk of ESRD by age 30 is 90% for deletions and nonsense mutations of COL4A5, 70% for splicing mutations, and 50% for missense mutations.