Christianson syndrome (OMIM 300243), caused by mutations in the X-linked SLC9A6 
gene, is characterized by severe global developmental delay and intellectual 
disability, developmental regression, epilepsy, microcephaly and impaired ocular 
movements. It shares many common features with Angelman syndrome. Carrier 
females have been described as having learning difficulties with mild to 
moderate intellectual disability, behavioural issues and psychiatric illnesses. 
There is little literature on the carrier female phenotype of Christianson 
syndrome. We describe a large extended family with three affected males, four 
carrier females, one presumed carrier female and one obligate carrier female 
with a c.190G>T, p.E64X mutation known to cause a premature stop codon in 
SLC9A6. We characterize and expand the clinical phenotype of female SLC9A6 
mutation carriers by comparing our described family with female carriers 
previously discussed in the literature. In particular, we highlight the 
neurodevelopmental and psychiatric phenotypes observed in our family and 
previous reports.