MECP2 and Rett syndrome: According to available databases, these four rare MECP2 variants identified in CPP girls have not been associated with Rett syndrome phenotype, except for one case with the p.Arg97Cys variant (https://www.ncbi.nlm.nih.gov/clinvar/variation/424578/?oq=rs1064797047&m=NM_001110792.2(MECP2):c.289C%3ET%20(p.Arg97Cys).