Before starting allopurinol in a patient of Han Chinese descent, screening for which marker is recommended because of its strong association with severe cutaneous adverse reactions such as Stevens-Johnson syndrome?

• A HLA-B*1502
• B HLA-B*5701
• C TPMT deficiency genotype
• D HLA-B*5801 ✓

Explanation

Allopurinol hypersensitivity syndrome (DRESS, SJS, TEN) is strongly associated with HLA-B*5801, particularly in Han Chinese, Thai and Korean populations, so testing is advised before initiating therapy in these groups. HLA-B*1502 predicts carbamazepine-induced SJS, HLA-B*5701 predicts abacavir hypersensitivity, and TPMT status relates to thiopurine myelotoxicity, making these distractors category-matched but wrong drugs.

Reference: Goodman and Gilman's The Pharmacological Basis of Therapeutics, 14th ed.

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