What is DDX3X?

First, DDX3X is a de novo mutation in Emelyn, which means it’s new and not inherited. There are many other diagnoses that can fall into the bucket of de novo, such as Down Syndrome. It basically means that an error occurred at conception and is unlikely to occur again for us. In other words, she did not inherit it from Patrick or myself and nothing that happened in my pregnancy led to Emelyn’s delays. While this wasn’t a question we were dwelling on, it was reassuring to hear.

If you haven’t heard of DDX3X, there’s good reason, it’s a very new discovery. The results of the first study were just published in The American Journal of Human Genetics on August 6, 2015 not long after the discovery. Our genetic counselor was able to provide the report to us and while most of it is way over our heads, it was very helpful in understanding Emelyn's diagnosis, especially since there is very little on the internet about it.

Between the genetic counselor and the report, we learned the DDX3X mutation is on the X chromosome and therefore almost only affects females. Males can also have the DDX3X mutation, but they must inherit it from their mother who is a carrier. In the 38 females identified with the this mutation in the study, their symptoms include: mild-to-severe intellectual disability, developmental delay, hypotonia, epilepsy, dysmorphic facial features, microcephaly, movement disorders, behavior problems, and abnormalities on brain MRIs. While Emelyn doesn’t fit all of these, she certainly fits the majority of them.

There isn't a name for Emelyn's diagnosis, but there may soon be. It's also unclear how prevalent the disorder is; while it appears there are less than 100 women diagnosed with the disorder, the numbers seem to be climbing daily. There is still much to learn about this diagnosis.

The American Journal of Human Genetics 97, 343-352, August 6, 2015.


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