FECD3 is a subtype of Fuchs endothelial corneal dystrophy (FECD) associated with an intronic heterozygous CTG expansion in TCF4. Presence of more than 40 repeats is associated with significantly increased risk of FECD64 but the expansion is incompletely penetrant. The gene discussed is TCF4; the disease is Fuchs endothelial corneal dystrophy.