Christianson syndrome is an X linked syndrome associated with intellectual disability, microcephaly, seizures, ataxia and absent speech.
Presentation
Onset of symptoms is normally within the first year of life with truncal
ataxia
Ataxia is a neurological sign consisting of lack of voluntary coordination of muscle movements that can include gait abnormality, speech changes, and abnormalities in eye movements. Ataxia is a clinical manifestation indicating dysfunction of ...
and
seizure
An epileptic seizure, informally known as a seizure, is a period of symptoms due to abnormally excessive or synchronous neuronal activity in the brain. Outward effects vary from uncontrolled shaking movements involving much of the body with l ...
s. The head is small (
microcephaly
Microcephaly (from New Latin ''microcephalia'', from Ancient Greek μικρός ''mikrós'' "small" and κεφαλή ''kephalé'' "head") is a medical condition involving a smaller-than-normal head. Microcephaly may be present at birth or it ...
). Common facial abnormalities include:
* Long narrow face
* Prominent nose
* Prominent jaw
* Large ears
* Open mouth
* Thick eyebrows
Other common features include:
* Uncontrolled drooling
* Abnormal eye movements
The associated intellectual disability is usually in the profound range.
Those affected often have a happy demeanor with frequent smiling and spontaneous laughter.
Genetics
This condition is caused by mutations in the ''
SLC9A6'' gene. This gene is located on the long arm of the
X chromosome
The X chromosome is one of the two sex-determining chromosomes (allosomes) in many organisms, including mammals (the other is the Y chromosome), and is found in both males and females. It is a part of the XY sex-determination system and XO sex ...
(Xq26.3). The gene encodes a
sodium
Sodium is a chemical element with the symbol Na (from Latin ''natrium'') and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 of the periodic table. Its only stable ...
/
hydrogen
Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic ...
exchanger located in the
endosome
Endosomes are a collection of intracellular sorting organelles in eukaryotic cells. They are parts of endocytic membrane transport pathway originating from the trans Golgi network. Molecules or ligands internalized from the plasma membrane can ...
s. Mutations in this gene cause a rise in the pH of the endosomes.
How this causes the clinical features is not known presently. The inheritance of this condition is X-linked dominant.
Diagnosis
The diagnosis may be suspected on clinical grounds. It is made by sequencing the SLC9A6 gene.
Differential diagnosis
*
Angelman syndrome
*
Spinocerebellar ataxia type 29
Management
There is presently no curative treatment. Management is supportive.
Epidemiology
The prevalence is not known but this is considered to be a rare disease.
History
This condition was first described in 1999.
[Christianson AL, Stevenson RE, van der Meyden CH, Pelser J, Theron FW, van Rensburg PL, Chandler M, Schwartz CE (1999) X linked severe mental retardation, craniofacial ]dysmorphology
Teratology is the study of abnormalities of physiological development in organisms during their life span. It is a sub-discipline in medical genetics which focuses on the classification of congenital abnormalities in dysmorphology. The relate ...
, epilepsy, ophthalmoplegia, and cerebellar atrophy in a large South African kindred is localised to Xq24-q27. J Med Genet 36:759–766 The causative mutation was discovered in 2008.
[Gilfillan GD, Selmer KK, Roxrud I, Smith R, Kyllerman M, Eiklid K, Kroken M, Mattingsdal M, Egeland T, Stenmark H, Sjøholm H, Server A, Samuelsson L, Christianson A, Tarpey P, Whibley A, Stratton MR, Futreal PA, Teague J, Edkins S, Gecz J, Turner G, Raymond FL, Schwartz C, Stevenson RE, Undlien DE, Strømme P (2008) SLC9A6 mutations cause X-linked mental retardation, microcephaly, epilepsy, and ataxia, a phenotype mimicking Angelman syndrome. Am J Hum Genet 82:1003–10]
References
{{Medicine, state=collapsed
Rare syndromes