Gout vs PsA — SCE Dermatology MCQ

Correct answer: D — Gout requires urate-lowering therapy and acute anti-inflammatory treatment; PsA flare requires disease-modifying therapy — misdiagnosis leads to inappropriate treatment. Joint aspiration with polarised light microscopy (negatively birefringent urate crystals) is definitive

The correct answer is D: gout requires urate-lowering therapy and acute anti-inflammatory treatment, while PsA flare requires disease-modifying therapy, and misdiagnosis leads to inappropriate treatment, with joint aspiration and polarised light microscopy showing negatively birefringent urate crystals being definitive. Gout and PsA both commonly affect the first MTP joint and can coexist, so an acute hot swollen toe in a known PsA patient is genuinely ambiguous clinically. Hyperuricaemia does not confirm gout here because PsA itself raises serum urate through increased epidermal cell turnover, making an elevated uric acid a red herring. NICE guidance identifies synovial fluid aspiration and microscopy as the gold standard when gout diagnosis is uncertain, directly visualising needle-shaped, negatively birefringent monosodium urate crystals. Treating a PsA flare with urate-lowering therapy achieves nothing, while treating true gout with escalated DMARDs or biologics adds unnecessary immunosuppression without addressing the crystal arthropathy.

Reference: https://www.nice.org.uk/guidance/conditions-and-diseases/skin-conditions