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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. A mutation in the HLA-A*3101 gene can lead to hypersensitivity reactions as a result of a 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).

Carbamazepine and the HLA-A*3101 gene

As a result of genetic variations, your body may not produce certain proteins or may produce them with an abnormal composition, potentially changing the way in which drugs are processed.

It is known, for example, that mutations in the HLA-A*3101 gene may be partly responsible for triggering a hypersensitivity reaction to a carbamazepine treatment. If you are HLA-A*3101 positive, your risk of experiencing (generally mild) side effects is significantly increased.

Information about your genetic predisposition may therefore provide grounds for extra vigilance in relation to a treatment with carbamazepine.

Read more about Carbamazepine »

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. For people of European origin 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. 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 (Clinical Pharmacogenetics Implementation Consortium) recommends 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.
At iGene we determine the following genotypes:

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

For this we use the marker rs1061235.

* In the case of Asians there is also a link to the HLA-B*1502 gene. If a person is HLA-B*1502 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. The occurrence of side effects has been studied and demonstrated primarily in Asian populations, as HLA-B*1502 positivity is much more common in Asians than in Europeans.