De novo MECP2 disomy in a Mexican male carrying a supernumerary marker chromosome and no typical Lubs syndrome features

A brief history of MECP2 duplication syndrome: 20-years of clinical understanding

MECP2 duplication syndrome (MDS) is a rare, X-linked, neurodevelopmental disorder caused by a duplication of the methyl-CpG-binding protein 2 (MECP2) gene-a gene in which loss-of-function mutations lead to Rett syndrome (RTT). MDS has an estimated live birth prevalence in males of 1/150,000. The key features of MDS include intellectual disability, developmental delay, hypotonia, seizures, recurrent respiratory infections, gastrointestinal problems, behavioural features of autism and dysmorphic features-although these comorbidities are not yet understood with sufficient granularity. This review has covered the past two decades of MDS case studies and series since the discovery of the disorder in 1999. After comprehensively reviewing the reported characteristics, this review has identified areas of limited knowledge that we recommend may be addressed by better phenotyping this disorder through an international data collection. This endeavour would also serve to delineate the clinical overlap between MDS and RTT.

Clinical and molecular genetic characterization of familial MECP2 duplication syndrome in a Chinese family

Background

Chromosomal duplication at the Xq28 region including the MECP2 gene, share consistent clinical phenotypes and a distinct facial phenotype known as MECP2 duplication syndrome. The typical clinical features include infantile hypotonia, mild dysmorphic features, a broad range of neurodevelopmental disorders, recurrent infections, and progressive spasticity.

Methods

This Chinese MECP2 duplication syndrome family includes six patients (five males and one female), and four asymptomatic female carriers. Two kinds of chips including 4x180K CNV + SNP chip and custom 8x60K CNV chip were used to detect MECP2 duplication, and then fluorescent in situ hybridization (FISH) analysis was performed to identify the exact copy number of MECP2. X-chromosome inactivation (XCI) analysis on AR gene was detected for all female family members, and the microsatellite analysis on MECP2 was used to validate the recombination event on MECP2 region.

Results

The affected male subjects presented with a broad range of neurodevelopmental symptoms (severe intellectual disability, developmental delay, seizure, language deficit, and autism spectrum disorder) as well as facial dysmorphism and other symptoms which were consistent with that of Western patients previous reported. Seizure is reported in Chinese patients for the first time. In addition, we validated three recombination events for the MECP2-duplication allele during maternal transmission due to X homologous recombination.

Conclusions

We provided the largest known Chinese pedigree with MECP2 duplication syndrome. The detailed clinical description and molecular genetic characterization in all affected family members further delineate the typical phenotype of this genomic disorder in Chinese population.

Electronic supplementary material

The online version of this article (10.1186/s12881-017-0486-4) contains supplementary material, which is available to authorized users.