Of the 15 discordant patients with NMD results, only 4 had a family history of ADPKD, whereas secondary genetic analysis by multiplex ligation-dependent probe amplification confirmed 8 NMD cases and 7 cases with one of the following: COL4A1, COL4A3, COL4A4, UMOD, UGGT2, and ALG8. This evidence concerns the gene COL4A4 and autosomal dominant polycystic kidney disease.