Fuchs endothelial corneal dystrophy (FECD) is a common, familial trait. Several genes have been associated with the disease, including LOXHD1, SLC4A11, TCF4, ZEB-1 and COL8A2 which has been identified as a cause of an early-onset Fuchs-like disease. The evidence for these genetic associations will be reviewed and new data will be shared. To date, the most sensitive biomarker for FECD is an intronic TGC trinucleotide expansion in the TCF4 gene which is present in the majority of FECD cases and in a small proportion of normal control subjects. Within families, this tricnucleotide expansion tends to segregate with the disease phenotype. The biology of trinucleotide expansion diseases and possible mechanisms by which TGC expansion may conribute to FECD will be presented. A brief discussion of recent advances in our understanding of the pathophysiology of FECD, such as the unfolded protein response and oxidative stress, will also be presented in order to highlight the challenges in linking the implicated causative genes with the biochemical pathways involved in the disease.