FMR1 and atypical Rett syndrome: Furthermore, aberrant DNA methylation profiles are known to be associated with many different human diseases, including Rett syndrome (Amir et al., 1999) and cancer (Kulis and Esteller, 2010), where there are alterations of global DNA methylation patterns, and Fragile X syndrome (FXS), where there is specific methylation of the CCG repeat mutation in the fragile X mental retardation-1 (FMR1) gene (Naumann et al., 2009).