What else is it called?
- Cerebral Cholesterinosis
- Sterol-27-hydroxylase deficiency
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What causes it?
CTX is caused by mutations in the CYP27 gene resulting in deficient activity of chemical sterol-27-hydroxylas which is important in initiating the Bile Acid Synthesis (BAS) pathway. This means that bile acid synthesis is disrupted, creating a build–up of cholesterol and cholestenol causing the degenerative problems described.
How common is it?
Worldwide, this disorder affects approximately 1 person in every 1,000,000. There is a much higher incidence rate in the Moroccan Jewish population where it affects 1 in every 108 individuals. CTX is also more prevalent in Asians with an incidence of 1 in every 70,000. In Europe, CTX affects between 1 in every 134,970 to 1 in every 461,358.
What are the signs and symptoms?
A common first sign of CTX is neonatal cholestastatic (reduction or stoppage of bile flow) jaundice, shown as yellowing of the skin and whites of the eyes, itchy skin, dark urine and light-coloured, foul-smelling stools. Chronic diarrhoea and liver dysfunction may also occur. Children with CTX often suffer from cataracts. Xanthomas (yellowish, cholesterol-rich deposits showing abnormal storage of fats and occurring anywhere on the body,) are common on the elbow, hand, patella, neck and Achilles tendon.
While some intellectual impairment may be noticed in childhood, this is more common from puberty onwards. Dementia, psychiatric disturbances and nerve damage progress with age, with dementia often happening in a person’s twenties alongside behavioural changes. These changes may include hallucinations, aggression, depression and suicidal tendencies.
Life expectancy without treatment is around 50-60 years, with some deaths reported in infancy.
How is it diagnosed?
A doctor will be able to diagnose a person with this disorder through a clinical evaluation, which includes a detailed genetic family history, identifying characteristic findings and conducting biochemical examinations on their blood and urine. A doctor will be able to conduct molecular genetic testing to confirm the diagnosis of CTX. The biochemical examinations include looking at how much cholestanol, plasma bile and bile alcohol is within your blood.
Can it be treated?
Treatment of CTX is possible through CDCA (chenodeoxycholic acid) replacement therapy, which can halt and even reverse symptoms. Cholic acid treatment is another alternative treatment.
Patients in the UK should refer to the NHS Clinical Commissioning Policy: Cholic acid and chenodeoxycholic acid for treating inborn errors of bile acid synthesis (all ages)
Do my family need to be tested?
CTX is an autosomal recessive inherited metabolic condition. For an autosomal recessive condition to be passed down to the child, the child must inherit two faulty enzyme making genes. Humans are made up of DNA, DNA is made up of chromosomes. Genes are sections of DNA that provide instructions to the body to make a certain protein. If there is a problem with the gene, then that protein will not be made correctly. Humans inherit genes from their parents via chromosomes found in the sperm from the father and chromosomes found in the egg from the mother. The parents don’t have to have cerebrotendinous xanthomatosis in order to pass it onto their children, they can be carriers. Carriers are people who have one faulty gene and one working gene, they don’t have the disorder because they have one working gene.
If both the parents are carriers, then the risk of each pregnancy is as follows:
- 25% chance that they will be affected by CTX
- 25% chance that they will not be affected by CTX and not be a carrier
- 50% chance that they will be a carrier and will not be affected by CTX
Thank you to Alex TLC for helping provide this up-to-date information.
Established in 2004, Alex TLC provides support for all those with a genetic leukodystrophy and are also an internationally recognised centre of excellence for those affected with adrenoleukodystrophy and adrenomyeloneuropathy.
Alex TLC Contact Details:
- Phone 020 7701 4388
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