COL4A5 and Alport syndrome: Alport syndrome (AS) is an inherited disorder caused by mutations in the COL4A5 (OMIM 303630), COL4A4 (OMIM 120131), and COL4A3 (OMIM 120070) genes, which compromise the integrity of the type IV collagen network within the glomerular basement membrane (GBM), leading to X-linked, autosomal, or digenic patterns of inheritance [12,13].