Which genetic marker is associated with increased risk for SJS/TEN?

• A. HLA-B*1502
• B. HLA-B*5701
• C. HLA-DR4
• D. HLA-B*2705

Answer: (A)

Genetic susceptibility to severe drug reactions like SJS/TEN can be driven by specific HLA alleles. The immune system presents drug-derived peptides on HLA molecules, and certain alleles can present these drug-related antigens in a way that triggers a cytotoxic T-cell attack on keratinocytes, leading to SJS/TEN.

HLA-B*1502 is the allele most strongly linked to carbamazepine-induced SJS/TEN, especially in people of Han Chinese and some Southeast Asian descent. This association means carriers who take carbamazepine have a markedly higher risk, which is why genetic testing is used in these populations to guide safer treatment choices or select alternative medications.

The other markers are linked to different contexts: HLA-B5701 is associated with abacavir hypersensitivity, not SJS/TEN with anticonvulsants; HLA-DR4 is linked to autoimmune conditions like rheumatoid arthritis and some types of diabetes; HLA-B2705 relates to the broader HLA-B27 group and spondyloarthropathies rather than carbamazepine-induced SJS/TEN.