title: The expanding phenotypic spectrum of female SLC9A6 mutation carriers: a case series and review of the literature.
abstract: 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.
authors.affiliation: Division of Clinical and Metabolic Genetics, The Hospital for Sick Children, Toronto, Canada.
authors.forename: Pierre
authors.initials: P
authors.lastname: Sinajon
authors.affiliation: Clinical Genetics, Lakeridge Health, Oshawa, Canada.
authors.forename: Deborah
authors.initials: D
authors.lastname: Verbaan
authors.affiliation: Clinical Genetics, Lakeridge Health, Oshawa, Canada. joyce.so@utoronto.ca.|The Fred A. Litwin Family Centre in Genetic Medicine, University Health Network and Mount Sinai Hospital, 60 Murray Street, Box 34, Toronto, ON, M5T 3L9, Canada. joyce.so@utoronto.ca.|Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Canada. joyce.so@utoronto.ca.
authors.forename: Joyce
authors.initials: J
authors.lastname: So
mesh_terms: D017204:Angelman Syndrome / Q000235:genetics* / Q000503:physiopathology; D001259:Ataxia / Q000235:genetics* / Q000503:physiopathology; D018389:Codon, Nonsense / Q000235:genetics; D004827:Epilepsy / Q000235:genetics* / Q000503:physiopathology; D005260:Female; D040181:Genetic Diseases, X-Linked / Q000235:genetics* / Q000503:physiopathology; D006579:Heterozygote; D006801:Humans; D008607:Intellectual Disability / Q000235:genetics* / Q000503:physiopathology; D007859:Learning Disabilities / Q000235:genetics / Q000503:physiopathology; D008297:Male; D008831:Microcephaly / Q000235:genetics* / Q000503:physiopathology; D009154:Mutation; D015835:Ocular Motility Disorders / Q000235:genetics* / Q000503:physiopathology; D010375:Pedigree; D017923:Sodium-Hydrogen Exchangers / Q000235:genetics*
chemical_list: D018389:Codon, Nonsense; C445316:SLC9A6 protein, human; D017923:Sodium-Hydrogen Exchangers