Genes tested in pharmacogenetics
Genes serve as the instructions our bodies use to develop, grow and function throughout our life. In pharmacogenetics (PGx), genes are tested for their association with predicted medication response. Genetic variations found in these genes can affect how the body responds to certain medications, influencing the medication’s potential side effects.
What are HLAs?
HLAs are a set of genes that provide instructions for producing HLA proteins, which are essential to the immune system. HLA proteins act like name tags on the surface of cells, allowing the immune system to distinguish between the body’s own cells and potential threats such as viruses or bacteria. This recognition process helps the immune system protect the body from infections and other harmful invaders.
PGx testing of HLAs
Genetic variation—the natural differences in DNA sequences between individuals—can affect how different people process the same medication.
Because of specific genetic variation, HLA proteins may work differently from person to person. HLA proteins can cause reactions to certain medications if the immune system believes a drug to be an invader in the body. Specifically, HLA variations can increase the risk of developing a few syndromes including Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) after being exposed to certain medications.
The results of HLA PGx testing can show how safe a medication might be for your child, which can help their health-care team choose or adjust their medication and dosage.
Medications affected by HLAs
Currently, there are many different medication classes and types that are affected by genetic variation in HLAs. If your child’s HLA proteins are not able to distinguish between the body’s own cells and potential threats, your child may experience strong immune responses to these medications:
- Anticonvulsants – medications to help prevent seizures
- Fosphenytoin/Phenytoin
- Carbamazepine
- Oxcarbazepine
- Fosphenytoin/Phenytoin
- Medications that reduce acid in urine to treat gout
- Medications that treat human immunodeficiency virus (HIV)
- Abacavir
The medications listed above are referred to by their generic names. You may hear your child’s medication called by a different brand name. Generic medicines and brand-name medicines share the same active ingredient and offer the same performance, safety and effectiveness. This medication list is also subject to change with increasing research on HLA.
HLA status
There are two different status groups for HLAs:
- HLA-positive – some medications might cause a strong immune response
- Your child’s health-care team may recommend switching to a different medication to ensure it works safely and effectively for your child.
- Your child’s health-care team may recommend switching to a different medication to ensure it works safely and effectively for your child.
- HLA-negative – the chance of having reactions to certain medications is the same as the average population
- Most medications should work as expected at standard doses.
- Most medications should work as expected at standard doses.
These statuses are not an indicator of your child’s health—they simply predict whether your child might need a different dose of medication or a different medication entirely. In addition to PGx test results, your child’s health-care team will still consider medical history and other factors to ensure the best treatment for your child.
To learn more about how genes relate to medication use, see Genetics basics for pharmacogenetics.
Why is my child’s gene group important?
HLA proteins can cause hypersensitivity reactions to certain medications if the immune system believes a drug to be an invader in the body. Think of the immune system like a security guard at a concert. If the guard recognizes someone on the guest list, they let them in without a problem. But, if they don’t recognize a person, they might stop them at the door or even call for backup if they think the person is a threat.
Similarly, in your child’s body, if they are HLA-positive, their immune system may mistake certain medications for harmful intruders. Instead of allowing the drug to help, the body 'sounds the alarm' and reacts strongly, which can make your child feel unwell.