However, the common differentials include Rett and Angelman syndromes [12] Although Rett syndrome is caused by mutations in the methyl-CpG-binding protein 2 (MECP2) it is not associated with a DNA methylation signature and though methylation changes occur in a subset of Angelman syndrome patients, these are generally limited to the imprinted SNURF:TSS-DMR at chromosome 15q11q13 [33, 34]. Here, MECP2 is linked to atypical Rett syndrome.