This information is provided by the National Institutes of Health (NIH) Genetic and Rare Diseases Information Center (GARD).
Christianson syndrome is an X-linked syndrome associated with intellectual disability, microcephaly, seizures, ataxia, and absent speech. Many individuals with this condition have a happy demeanor with frequent smiling and unprovoked laughter, similar to those with Angelman syndrome. Christianson syndrome is caused by mutations in the SLC9A6 gene, which is located within the q24-q27 interval of the X chromosome. There appears to be a range of phenotypes in carrier females, from intellectual disability to absence of symptoms.
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