Forty-two individuals (male 61.9%) had a genetic diagnosis of X-linked Alport syndrome (XLAS) due to pathogenic or likely pathogenic variants in COL4A5. Amongst the 42 variants in COL4A5, missense variants affecting the glycine residue were observed in 24 individuals (57.1%), followed by splicing variants in 8 individuals (19.0%), nonsense (loss of function) variants in 6 individuals (14.3%), frameshift variants in 3 individuals (7.1%) and in-frame deletion variants in one individual (2.4%). This evidence concerns the gene COL4A5 and X-linked hydrocephalus with stenosis of the aqueduct of Sylvius.