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Example clinical scenario

A 25-year-old man requires carbamazepine for the treatment of epilepsy. He has been tested previously and was found to have the HLA-B*15:02 allele.

What do you need to know?

  • Variants in the HLA-B*15:02 and HLA-A*31:01 alleles are associated with an increased risk of severe cutaneous and hepatic adverse reactions (such as Stevens-Johnson syndrome) in patients treated with carbamazepine.
  • While severe cutaneous reactions are estimated to occur in between 1 and 6 per 10,000 new users of carbamazepine in countries with mainly White populations, the risk in some Asian populations is thought to be up to 10 times higher. Associations between HLA-B*15:02 and HLA-A*31:01 and carbamazepine hypersensitivity have been recorded in children as well as in adults.

What do you need to do?

  • Pharmacogenomic test results should be used as follows.
    • Carbamazepine-naive patients who test positive for HLA-B*15:02: do not prescribe carbamazepine.
    • Patients who have received carbamazepine consistently for longer than three months and test positive for HLA-B*15:02: cautiously consider prescribing carbamazepine.
    • Carbamazepine-naive patients who test positive for HLA-A*31:01: do not prescribe carbamazepine unless no alternative treatment options exist.
      • If no alternative treatment options exist, consider the use of carbamazepine with increased frequency of clinical monitoring and discontinue carbamazepine at the first sign of a cutaneous adverse reaction.
    • Patients who have received carbamazepine consistently for longer than three months and test positive for HLA-A*31:01: cautiously consider prescribing carbamazepine.
  • It should be noted that not all carbamazepine-induced cutaneous or hepatic adverse reactions can be attributed to HLA-B*15:02 or HLA-A*31:01. All patients should be monitored as standard practice.
  • For more information about genomic testing for HLA-B*15:02 and HLA-A*31:01 variants, including how identification of variants affects patient management, see our Knowledge Hub resource, Carbamazepine.
  • For information about how to arrange testing in Wales, Scotland or Northern Ireland, see our dedicated Knowledge Hub resource.

Resources

For clinicians

References:

For patients

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  • Last reviewed: 02/07/2024
  • Next review due: 02/07/2025
  • Authors: Fan Cheng, Nicola Husain
  • Reviewers: Dr Charlotte Barker, Professor Bill Newman