About DDx3x

DDX3X Syndrome is a rare disease caused by a spontaneous mutation within the DDX3X gene at conception or can be inherited. The syndrome was discovered in the United States in 2014 and primarily affects girls due to its location on the X-chromosome, though there are some boys it has affected as well. Although it has only been identified in about over 1000 individuals, doctors believe it is the cause of 1 to 3 percent of all intellectual disabilities in females. 

DDX3X Syndrome is often misdiagnosed as autism spectrum disorder, cerebral palsy, Rett Syndrome, Dandy-Walker Syndrome, or a generic developmentally delayed label. It is linked to intellectual disabilities, seizures, autism, low muscle tone, abnormalities of the brain, and slower physical developments. It has a broad spectrum—some individuals develop the ability to speak in full sentences, while others are nonverbal. Some individuals run, jump, and even ski, while others are unable to walk. 

A simple and comprehensive summary of DDX3X Syndrome is available in this document from RareChromo.org. For more information read the DDX3X Manuscript.

“I left that night feeling connected to these families and their children, and I knew I would never see my research the same way.”

Mariah Hoye

a Regeneration Next Fellow and Postdoctoral Research associate in the laboratory of Debra Silver, on her experience at the 4th annual DDX3X foundation meeting.

Do you think your child could have DDX3X Syndrome?

Not all individuals with DDX3X Syndrome are affected in the same ways, however, the following are common symptoms:

  • Intellectual disability
  • Developmental delays
  • Low muscle tone/hypotonia
  • Difficulty with speech
  • Epilepsy/seizures
  • Movement disorders
  • Abnormalities of the brain
  • Microcephaly

The DDX3X mutation can be identified through Whole Exome Sequencing (WES)—a test that sequences the protein-coding regions of the 20,000 genes in an individual, as well as more targeted panel analysis, such as the Congenital Hypotonia Xpanded Panel offered by GeneDx, which targets the specific phenotype-driven gene list for hypotonia/low muscle tone. WES and more targeted panel testing are becoming more readily available, affordable, and common for the diagnosis of conditions believed to have a genetic basis.

GeneDx, a Maryland-based genetic testing company, was one of the first laboratories to identify the DDX3X gene and the association between alterations in this gene and intellectual disabilities. It is one of several clinical laboratories that does WES and panel testing based on specific conditions, such as hypotonia. Testing by WES or a specific gene panel must be requested by a doctor and the results sent to a medical facility. Families interested in genetic testing should discuss this option with their doctor, who may recommend genetic counseling and a genetics evaluation to determine if WES or a specific panel test is the appropriate diagnostic test to pursue.

Learn more about our Foundation, including the work we do to support those affected by DDX3X Syndrome and those researching it.


Frequently Asked Questions

The information is handled according to the Terms and Conditions . In short, the information is compiled together to create research-friendly data for medical and genetic researchers.

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Yes! Check out this awesome summary from Unique (rarechromo.org).


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