The MECP2 duplication syndrome is a rare disorder that is caused by the duplication of a chromosomal fragment on the X chromosome, namely, chromosome Xq28, including the entire MECP2 gene.
The core features consist of early infantile hypotonia, delayed motor and speech development, severe intellectual disability, epilepsy and proneness to infections.
It is inherited in an X-linked fashion and mostly affects boys. However, several girls with the disorder have been described.
The overall prevalence of this condition is estimated to be 1% of unexplained X-linked intellectual disability.