Allopurinol hypersensitivity — SCE Rheumatology MCQ

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ModerateCrystal ArthropathiesAllopurinol hypersensitivitySCE Rheumatology

A 67-year-old man of Han Chinese ancestry starts allopurinol for gout and 3 weeks later develops fever, facial oedema, widespread rash, eosinophilia and acute kidney injury. ALT is elevated. There are no urate crystals in the current joint aspirate. What is the most likely diagnosis?

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Correct answer: B — Allopurinol hypersensitivity syndrome

Explanation lettering: C = shown as A · E = shown as C · A = shown as D · D = shown as E

Allopurinol hypersensitivity syndrome is best because fever, rash, eosinophilia, hepatitis and renal injury after allopurinol initiation indicate allopurinol hypersensitivity syndrome. A is less suitable because septic arthritis would localise to infected joint and cultures; C is less suitable because reactive arthritis follows infection and does not cause DRESS-like illness; D is less suitable because PsA does not explain temporal relationship to allopurinol; E is less suitable because an acute gout flare would not cause systemic rash with eosinophilia and hepatitis. Clinical pearl: certain ancestry groups have higher HLA-B*58:01-associated risk, which may influence pre-treatment testing.

Reference: BNF; NICE NG219