TCF4 and Fuchs endothelial corneal dystrophy: To date, it has been suggested as a viable way to detect STR expansions and contractions associated with a subset of neurological and neuromuscular conditions.22, 23, 24, 25 Despite TCF4 being ubiquitously expressed, CTG18.1 expansions have only been robustly associated with FECD, a corneal endothelial cell-specific disease.