The study identified a common polymorphism, located within an intronic region of the TCF4 gene on Chromosome 18, that conferred up to a 30-fold increased risk for FECD.27 28 Two years later, the functional variant underlying this signal of association was identified: expansion of a non-coding intronic triplet repeat element (termed CTG18.1) within TCF4. The gene discussed is TCF4; the disease is Fuchs endothelial corneal dystrophy.