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Drug Hypersensitivity — SCE Dermatology MCQ

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HardDrug ReactionsDrug HypersensitivitySCE Dermatology

A 33-year-old woman with epilepsy on Carbamazepine develops a morbilliform drug eruption. She is found to be HLA-A*3101 positive. What is the significance of this HLA type?

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Correct answer: E — It is associated with increased risk of Carbamazepine hypersensitivity in European populations

HLA-A*3101 is associated with increased risk of Carbamazepine-induced hypersensitivity reactions (morbilliform eruption, DRESS, SJS/TEN) in European and Japanese populations. This is distinct from HLA-B*1502, which is associated with Carbamazepine-induced SJS/TEN specifically in Southeast Asian populations. Pharmacogenomic testing before prescribing Carbamazepine is recommended: HLA-B*1502 in Southeast Asian patients and HLA-A*3101 in European patients. HLA-B*5701 is tested before Abacavir (HIV); HLA-B*5801 before Allopurinol.

Reference: BAD 2019 Drug Eruption Guidelines; BNF; CPIC Guidelines