PTEN and Rett syndrome: These included 5% with a high-resolution chromosomal abnormality, 5% with fragile X syndrome, 5% with Rett syndrome, 3% with PTEN gene mutations, approximately 10% with other genetic syndromes (e.g., tuberous sclerosis), and 10% with structural genomic deletions or duplications using early versions of chromosomal microarrays.