Dysregulation of MeCP2, including altered recognition of 5hmC or misfunction of the MeCP2–HDAC complex, is implicated in neurodevelopmental disorders such as Rett syndrome, highlighting the critical role of MeCP2 as a reader of hydroxymethylation in maintaining proper neuronal gene expression and genomic stability [20]. This evidence concerns the gene MECP2 and atypical Rett syndrome.