Expansion of the CTG18.1 locus in the TCF4 gene makes FECD one of the most common tri-nucleotide repeat disorders along with myotonic dystrophy (DM1 and DM2), Huntington disease (HD), Spinocerebellar ataxia (SCA), Friedreich ataxia (FA) and Fragile X syndrome (FRAXA) [18]. This evidence concerns the gene TCF4 and Huntington disease.