In multivariate analysis with stepwise selection, the following 4 variables remained as independent predictors of the progression to kidney failure among patients with XLAS: sex, baseline proteinuria, baseline eGFR, and the pathogenic variants in COL4A5 (Table 2).2 This evidence concerns the gene COL4A5 and X-linked hydrocephalus with stenosis of the aqueduct of Sylvius.