COL4A5 and Alport syndrome: Alport syndrome (AS) (OMIM# 301050) is a clinically heterogeneous nephropathy caused by pathogenic variants in collagen IV genes (COL4A3 [MIM# 120070] [Ref Seq NM_000091.4], COL4A4 [MIM# 120131] [Ref Seq NM_000092.4], COL4A5 [MIM# 303630] [Ref Seq NM_000495.4]) with a prevalence of 1:5.000 despite a very high variability among the populations [1].