Here is a truly great resource. From Unique in the UK. The Unique organization describes themselves as follows:
Unique is a source of information and support to families and individuals affected by any rare chromosome disorder and to the professionals who work with them. Unique is a UK-based charity but welcomes members worldwide. Membership of Unique is free but the group receives no government funding and is heavily reliant on donations and fundraising to continue its work. Please help us in whatever way you can.
Unique provides an excellent 16- page guide on Xq28 Duplications (also known as MECP2 Duplication Syndrome). You can download a PDF version here. It contains a wealth of information but is written clearly in plain English.
Some of the literature is a bit dated. For example, they indicate that only about 60 cases have been reported in the medical literature, which is certainly no longer accurate, but most of it is accurate and thorough. This resource is highly recommended!