HLA-A*31:01

What is HLA-A*31:01?

HLA-A*31:01 is a variant of a human leukocyte antigen (HLA) gene, the system the immune system uses to present fragments of proteins — including drugs bound to proteins — to T cells. Particular HLA alleles bind particular drugs, which is why carrying one can turn an ordinarily safe medicine into a severe immune reaction, and why some alleles track autoimmune conditions.

HLA-A*31:01 is associated with DRESS rather than SJS/TEN (which is HLA-B*15:02). Different mechanism and clinical presentation.

How common is HLA-A*31:01?

Drug reactions linked to HLA-A*31:01

Carbamazepine Hypersensitivity (DRESS/maculopapular exanthema) high risk

HLA-A*31:01 carriers have increased risk of carbamazepine-induced DRESS and maculopapular exanthema. Consider alternative anticonvulsants (e.g., lamotrigine, levetiracetam). CPIC recommends HLA-A*31:01 testing before initiating carbamazepine in populations where this allele is common.
Evidence: CPIC Level A (Strong) · Source: CPIC Guideline for Carbamazepine and HLA-A/HLA-B (2018, updated 2024) · HLA-A*31:01 prevalence: ~2-5% in Europeans, ~5-10% in East Asians, ~1-2% in Africans.

Oxcarbazepine Hypersensitivity moderate risk

HLA-A*31:01 carriers may also have increased risk with oxcarbazepine. Monitor closely if prescribed.
Evidence: CPIC Level B (Moderate) · Source: CPIC Guideline for Carbamazepine and HLA-A/HLA-B (2018)

How is HLA-A*31:01 inferred from a consumer DNA file?

Consumer chips do not sequence HLA genes. HLA-A*31:01 is inferred from the tag SNP rs1061235 (risk allele A), which travels with the HLA allele on the same stretch of chromosome. How reliably it does so (r²) differs by ancestry:

A tag-SNP call is a probability, not a laboratory HLA type. A positive result that would change a prescription should be confirmed by clinical HLA typing.