Summary
Christianson syndrome is a very rare form of syndromic intellectual deficit characterized by microcephaly, severe developmental delay or regression, hypotonia, abnormal movements, and early-onset seizures.
The prevalence of Christianson syndrome is unknown. It is extremely rare and has been reported in six families to date (fewer than 30 individuals, primarily of Norwegian origin).
Affected males are reported to have profound intellectual disability, microcephaly, absence of speech, early-onset epilepsy of various types, abnormal movements, developmental delay and hypotonia. Other manifestations include ophthalmoplegia, truncal or gait ataxia, dystonia with stereotyped hand movements, frequent smiling with episodes of unprovoked laughter, autistic spectrum disorder, open mouth, profuse drooling and swallowing difficulties, gastroesophageal reflux and thin body habitus. Intellectual disability has been reported in some female carriers.
Various nonsense mutations and deletions in the SLC9A6 gene (Xq26.3) have been reported in patients with this syndrome. SLC9A6 encodes sodium/hydrogen exchanger protein 6 (NHE-6) which regulates the endoluminal pH of early endosomes and is involved in the trafficking of proteins essential for growth and maintenance of dendritic spines.
Magnetic resonance imaging (MRI) scan shows variable features including prominent cisterna magna, enlarged 4th ventricle, cerebellopontine and supracerebellar cisterna, hypoplasia/atrophy of the cerebellum (predominantly of the vermis) and pons, ventricular enlargement and sulcal widening due to brain atrophy, and thin corpus callosum. Elevated levels of glutamate/glutamine have been found in the basal ganglia of affected individuals. Molecular genetic testing is needed to confirm diagnosis.sis.
Differential diagnoses include Angelman syndrome, spinocerebellar ataxia type 29 (see these terms) and other X-linked forms of intellectual deficiencies.
Prenatal genetic testing is possible if the familial mutation is known.
Transmission appears to follows an X-linked semi-dominant pattern.
No specific treatment is available. Management is supportive.
The prognosis is poor with premature death at 25-30 years of age being reported in many cases.
Expert reviewer(s)
Last update: February 2013
