Rett syndrome is a genetic disease caused nearly 80% in typical cases and 30% of atypical forms by mutations in the MECP2 gene located in Xq28, which is a transcriptional repressor. Loss the function of the MeCP2 protein could cause overexpression of certain genes, which would be detrimental to the development of the central nervous system. This retrospective study compiled Laboratory of Medical Genetics and oncogenetic CHU Hassan II of Fez on 8 patients aged between 2 and 11 years on suspicion of Rett syndrome during a period of 3 years from January 2010 to December 2012. Molecular analysis of the DNA of these patients is to highlight the presence of deleterious mutations of the MECP2 gene. At the end of this study, we found the following results: The diagnosis of Rett syndrome is mainly based on the combination of several clinical signs in a very characteristic evolutionary context. Most of our patients are referred for psychomotor regression, microcephaly and stereotypic hand movements. Molecular exploration aims to highlight deleterious mutations of the MECP2 gene. In our series, only three of our patients with a mutation in the MeCP2 gene representing a coverage rate of Rett syndrome by about 38%. The presence of a mutation in the MECP2 gene provides better support for patients and their families in the area neuropediatric.