Hi! DD (4) has GDD and functions at around the level of a 2 year-old.
She has slightly dysmorphic features and her geneticist had varous tests done in her first three years to see if she could come up with a diagnosis.
One of those involved sending a sample off to Holland where research was being done on the 9th chromosone. Initially her results were normal but now a tiny deletion has been found on a gene called EHMT-1 and the adjacent gene, and apparently she is one of just 4 cases known about worldwide! We are hoping to meet them one day when the study is published and more info can be released.