Alterations in methyl CpG-binding protein (MECP)2, an X-linked gene involved in the regulation of RNA splicing and chromatin remodeling, were confirmed in approximately 95% of individuals diagnosed with RTT [3], while the others were confirmed in either cyclin-dependent kinase-like (CDKL)5 or forkhead box protein (FOXG)1 alterations as atypical cases of RTT [4,5]. Here, CDKL5 is linked to Rett syndrome.