COL4A5 and Alport syndrome: Approximately 80% of Alport syndrome patients are X-linked (XLAS) (OMIM # 301050) and because of mutations in the COL4A5 gene (located at position Xq22.3, OMIM 301050, RefSeq Z37153, HGNC 2207; NCBI reference sequence NM_000495.4) (Jais et al., 2000).