The CTG18.1 trinucleotide repeat expansion in the TCF4 gene has been detected in a large proportion of late-onset FECD patients and segregated in familial cases, so it is currently considered a causal variant (30, 45, 48, 50, 51, 55, 57–64). This evidence concerns the gene TCF4 and Fuchs endothelial corneal dystrophy.