Common features of Xq28 duplications in boys are as follows:
- Hypotonia (floppiness or low muscle tone) in babies and infants
- Delayed, limited or absent speech and language
- Learning (intellectual) disability
- Epileptic seizures in half of the patients
- Progressive spasticity (muscles are continuously contracted which causes tightness and stiffness and may interfere with walking and moving)
- Recurrent respiratory infections
Boys may also have other symptoms such as difficulty swallowing, bowel problems including constipation and reflux.
Some boys also display autistic behavior (including anxiety, stereotypic hand movements).
In the majority of cases, girls with an Xq28 duplication are not obviously affected by the duplicated DNA due to skewed X-inactivation. Girls who are affected by their Xq28 duplication normally show milder and more variable symptoms than affected boys.