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Am J Med Genet A. 2016 Aug;170(8):2103-10. doi: 10.1002/ajmg.a.37765. Epub 2016 Jun 3.

A new family with an SLC9A6 mutation expanding the phenotypic spectrum of Christianson syndrome.

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Centre de Génétique et Centre de Référence Anomalies du développement et Syndromes malformatifs, Hôpital d'Enfants, CHU Dijon, Dijon, France.
Fédération Hospitalo-Universitaire TRANSLAD, CHU Dijon et Université Fédérale de Bourgogne Franche Comté, Dijon, France.
Laboratoire "Mécanismes génétiques des maladies neurodéveloppementales", IGBMC, Illkirch, France.
Laboratoire de Diagnostic génétique, CHU Strasbourg, Strasbourg, France.
Centre Référent des Troubles du Langage et des Apprentissages, Hôpital d'Enfants, CHU Dijon, Dijon, France.
Service de neurologie pédiatrique, Hôpital Femme Mère Enfant, Hospices Civils de Lyon, Lyon, France.
Service de Pédiatre, Centre Hospitalier de Chalon-sur-Saône, Chalon-sur-Saône, France.
Centre de génétique et Centre de Référence Anomalies du développement et Syndromes malformatifs, AMU, APHM, Marseille, France.


Using targeted next generation sequencing, we have identified a splicing mutation (c.526-9_526-5del) in the SLC9A6 gene in a 9-year-old boy with mild intellectual disability (ID), microcephaly, and social interaction disabilities. This intronic microdeletion leads to the skipping of exon 3 and to an in-frame deletion of 26 amino acids in the TM4 domain. It segregates with cognitive impairment or learning difficulties in other members of the family. Mutations in SLC9A6 have been reported in X-linked Christianson syndrome associating severe to profound intellectual deficiency and an Angelman-like phenotype with microcephaly, absent speech, ataxia with progressive cerebellar atrophy, ophthalmoplegia, epilepsy, and neurological regression. The proband and his maternal uncle both have an attenuated phenotype with mild ID, attention deficit disorder, speech difficulties, and mild asymptomatic cerebellar atrophy. The proband also have microcephaly. The mutation cosegregated with learning disabilities and speech difficulties in the female carriers (mother and three sisters of the proband). Detailed neuropsychological, speech, and occupational therapy investigations in the female carriers revealed impaired oral and written language acquisition, with dissociation between verbal and performance IQ. An abnormal phenotype, ranging from learning disability with predominant speech difficulties to mild intellectual deficiency, has been described previously in a large proportion of female carriers. Besides broadening the clinical spectrum of SLC9A6 gene mutations, we present an example of a monogenic origin of mild learning disability.


Christianson syndrome; SLC9A6; cerebellar atrophy; learning disabilities; microcephaly

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