The CTG18.1 trinucleotide repeat expansion (>40–50 repeats) in the intron region of the TCF4 gene is thought to be causal for approximately two-thirds of late-onset FECD cases in the European ancestry population and has been confirmed in several independent cohorts, including the Russian cohort [8,13,14,15]. Here, TCF4 is linked to Fuchs endothelial corneal dystrophy.