DDX3X syndrome is caused by a spontaneous mutation at conception. Due to its location on the X-chromosome, it primarily affects girls, though there are affected boys. Doctors believe it is the cause of 1 to 3 percent of all intellectual disabilities in females. DDX3X syndrome is linked to intellectual disabilities, seizures, autism, low muscle tone, abnormalities of the brain, difficulties with speech, and slower physical developments. To learn more, visit ddx3x.org.