The c.471C>G (p.Phe157Leu) variant in MECP2 (NM_004992.3) has been reported in an individual with a clinical phenotype suggestive of Rett syndrome (PMID 15675358) (PP4). The p.Phe157Leu variant in MECP2 has been observed in 2 additional individuals with MECP2-related conditions (PMID 30536762, RettBASE) (PS4_moderate). The p.Phe157Leu variant occurs in the well-characterized methyl-DNA binding functional domain of the MECP2 gene (PM1). Computational prediction analysis tools suggests a deleterious impact; however, this information does not predict clinical significance on its own (PP3). The p.Phe169Leu variant in MECP2 is absent from gnomAD (PM2_supporting). The c.471C>A variant in the MECP2 gene results in a p.Phe157Leu change that is a previously established pathogenic variant (ClinVar, Invitae - internal database) (PS1). A pathogenic missense variant (p.Phe157Ile) has been previously identified within this codon which indicates that this residue is critical to the function of the protein (PMID 16832102, 27929079, RettBASE) (PM5). In summary, the c.471C>G (p.Phe157Leu) variant in MECP2 is classified as Pathogenic for Rett syndrome based on the ACMG/AMP criteria (PS1 + PM1 + PM5 + PS4_moderate + PM2_supporting + PP3 + PP4).