Rett syndrome (RTT) is an X-linked early-onset neurodevelopmental disorder that is predominantly caused by mutations of the methyl-CpG-binding protein 2 (MECP2) gene, which encodes a multifunctional epigenetic regulator (Amir et al., 1999; Castro et al., 2013). This evidence concerns the gene MECP2 and atypical Rett syndrome.