Current evidence shows that early-onset FECD is attributed to missense mutations in the extracellular matrix encoding gene COL8A2,3 while late-onset FECD is genetically heterogeneous.4 However, a significant majority of the late-onset cases have a shared underlying genetic cause of disease: expansion of a triplet repeat element (termed CTG18.1) situated within an intronic region of the transcription factor encoding gene TCF4. This evidence concerns the gene TCF4 and Fuchs endothelial corneal dystrophy.