An Xq28 duplication means that the cells of the body have an extra amount of genetic material from the Xq28 part of the X chromosome.
These duplications can be variable in size but those that are too small to be visible under the microscope are called microduplications.
In MECP2 duplication syndrome, the affected child carries two or more copies of the MECP2 gene that is located on Xq28. This will lead to a higher amount of the MECP2 protein. It has been proven that increased amount of MECP2 protein in the neurons of the brain lead to abnormal functioning.