Christianson syndrome is a genetic disorder marked by physical disability and intellectual disability. It is rare, newly discovered, and mostly affects boys. Christianson syndrome normally presents in infancy, where a small head size (microcephaly) and intellectual disabilities are apparent. The prevalence of this condition is unknown.
Definition & Facts
Christianson syndrome is passed down via X-inked recessive inheritance. It occurs due to genetic problems with the X chromosome. Because males have only one chromosome, an X chromosome, they are more likely to be afflicted. Females can have the syndrome, but it would be necessary for both X chromosomes to be affected. Women carry the trait and can pass it on to their children.
Symptoms & Complaints
Because the syndrome is progressive, the symptoms will continue to worsen with time. Other symptoms include:
- Poor feeding
- Difficulty reasoning or problems with logical thought
- Uncontrollable drooling due to a constantly open mouth
- Inability to communicate through words
- Swallowing difficulty
- Autism spectrum disorder characteristics
- A happy demeanor and bouts of spontaneous and unprovoked laughter
- Cerebellar atrophy, which means that instead of growing, the cerebellum remains the same size or shrinks
- Strabismus (in which the eyes do not look in the same direction) and nystagmus which are abnormal eye movements
- Narrow face
- Ataxia (loss of balance and coordination)
- Hyperkinesis (muscle spasms)
- Symptoms of Angelman syndrome
- Hypotonia (low muscle tone)
- Gastroesophageal reflux disease
- Low height and/or weight for age group
- Cerebellar vermis atrophy (particularly after first decade)
Sometimes female carriers of the genetic mutation that causes this syndrome experience mild intellectual disability, though a direct causal relationship still needs to be determined regarding this association.
Christianson syndrome results from a mutation on the SLC9A6 gene. This gene produces a protein called NHE6. This protein is found in the membrane that surrounds endosomes, a part of a cell that recycles proteins. When working correctly, this protein is involved in the process of sodium/hydrogen exchange which helps to maintain cell acidity (pH). It also helps proteins move to the proper locations within a cell, among other functions.
When the gene has experienced mutations, the NHE6 protein is too short, non functioning, or it breaks down in cells too quickly. Because of these abnormalities, it is unable to perform its function in regulating the pH in endosomes, and this results in abnormal pH levels in the endosomes. Somehow this dysfunctional process and result impacts neurological development and cognition, though the mechanisms have not been fully understood.
Diagnosis & Tests
Medical history, family history, symptom presentation, and a physical examination are all parts of the diagnostic process. Attaining a definitive diagnosis can be achieved through a molecular genetic test, which will show the genetic mutation.
Treatment & Therapy
Christianson syndrome is a newly discovered disorder about which much remains to be discovered. As such, there is currently no established treatment regimen available for Christianson syndrome. That being said, anticonvulsant drugs may be able to help mitigate seizures. Special education, occupational therapy, and physical therapy may address cognitive, intellectual, and neuromuscular impairment associated with this condition.
Prevention & Prophylaxis