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HLA (human leukocyte antigen) genes play an important role in the immune system. They help the immune system to identify and respond to foreign substances, such as bacteria and viruses.

Certain DNA variations in the HLA-A gene can lead to the so-called HLA-A*3101 allele. This specific HLA-A*3101 allele can lead to hypersensitivity reactions as a result of treatment with carbamazepine.

Carbamazepine is a drug that calms overstimulated nerves in the brain. It is used to treat epilepsy, manic depression, neuralgia, diabetes insipidus and alcohol withdrawal, amongst other things.

In around 10% of people treatment with carbamazepine triggers side effects in the form of skin problems. The severity and nature of these can vary. In patients who experience mild side effects red bumps and marks can appear on the skin, which spontaneously disappear once the medication is stopped.

However, severe side effects can also occur, such as itching, fever and inflammation of the liver or kidneys. These side effects are referred to by the term hypersensitivity syndrome (HSS/DRESS syndrome).

In rare cases a patient may even experience serious, sometimes life-threatening, side effects, such as Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN).

Genetic predisposition
Your individual risk of side effects in the event of treatment with carbamazepine may be partly explained by genetic variations. It is known, for example, that mutations in the HLA-A gene are partly responsible. It has been demonstrated that carriers of the HLA-A*3101 gene are genetically predisposed to carbamazepine hypersensitivity. HLA-A*3101 positivity, which significantly increases the risk of side effects, is found in around 4 to 10% of the European population and in 10 to 20% of the Asian population. Studies show that the risk of side effects is roughly 10 times greater in people who are HLA-A*3101 positive.*

For safety reasons, the CPIC and the KNMP recommend not starting a treatment with carbamazepine in the case of patients who are HLA-A*3101 positive. How you should ultimately proceed is a decision for an attending doctor.
The following genotypes are determined:

  • HLA-A*3101 positive
  • HLA-A*3101 negative

* There is also a link to the HLA-B*1502 and HLA-B*1511 alleles. If a person is HLA-B*1502 or HLA-B*1511 positive, they have an increased risk of serious side effects such as Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) as a result of a treatment with carbamazepine and related drugs like phenytoin and oxcarbazepine.

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