MECP2 duplication syndrome in both genders
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Updated: May 19, 2026

An Electrochemiluminescence-Based Assay for MeCP2 Protein Variants
Published on: May 22, 2020
Shino Shimada1, Nobuhiko Okamoto, Masahiro Ito
1Tokyo Women's Medical University Institute for Integrated Medical Sciences, Tokyo, Japan.
Background:
Duplications involving the methyl-CpG-binding protein 2 gene (MECP2) locus at Xq28 have been frequently identified in male patients who exhibit a phenotype unique from that of Rett syndrome, which is mainly characterized by severe mental retardation, recurrent infections, and epilepsy. This combination of features is recognized as MECP2 duplication syndrome.
Methods:
Genomic copy number was investigated for patients with unexplained mental retardation, and phenotypic features of the patients having interstitial duplications including MECP2 were analyzed.
Results:
Three male and one female patients with MECP2 duplication were identified. The phenotypic features of all the four patients were compatible with MECP2 duplication syndrome. The X-chromosome inactivation (XCI) pattern was analyzed in the female patient, identifying a skewed XCI that activated the X-chromosome containing the MECP2 duplication. Her mother possessed the same MECP2 duplication and a random XCI pattern but exhibited no phenotypic features, indicating a nonsymptomatic carrier. The brain magnetic resonance imaging revealed periventricular cystic lesions in all four patients, including the female patient.
Conclusion:
This study suggested clinical implications of the MECP2 duplication syndrome not only in the male but also in female patients with unexplained mental retardation.
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