HLA-B5801 Testing — SCE Rheumatology MCQ

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ModerateCrystal ArthropathyHLA-B5801 TestingSCE Rheumatology

A 35-year-old man of Han Chinese descent with gout is being considered for allopurinol. HLA-B*58:01 genotyping is requested before his first exposure to the drug. What is the principal purpose of this test?

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Correct answer: E — It predicts allopurinol hypersensitivity syndrome, including SJS/TEN

HLA-B*58:01 is a strong genetic risk marker for severe allopurinol hypersensitivity, including DRESS and Stevens–Johnson syndrome/toxic epidermal necrolysis. The allele is relatively prevalent in Han Chinese populations, so the UK allopurinol SmPC advises considering screening before treatment in such high-prevalence groups. If the allele is present, allopurinol should generally not be started unless there is no reasonable alternative and the anticipated benefit outweighs the risk. A negative result does not eliminate the possibility of severe hypersensitivity. The genotype does not determine the maximum dose, predict urate-lowering efficacy or indicate gout severity. It is not a pharmacogenetic test for febuxostat hypersensitivity.

Reference: Electronic Medicines Compendium. Allopurinol Tablets BP 100 mg, Summary of Product Characteristics, section 4.4: HLA-B*5801 allele. Updated 29 January 2025. https://www.medicines.org.uk/emc/product/7004/smpc