TCF4 and Fuchs' endothelial dystrophy: Our findings further highlight the importance of dysregulated ion balance in FECD and indicate a pleiotropic connection to kidney function at TCF4. In addition to the known association between the UACR PGS and FECD55, we found associations with PGSs for urinary sodium and urinary potassium, driven by shared signals at the TCF4 locus.