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Psoriatic Arthritis — RACP Adult Medicine MCQ

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ModerateRheumatologyPsoriatic ArthritisRACP Adult Medicine

A 45-year-old man presents with a red, warm, swollen knee. He has a history of psoriasis. Joint aspirate is sterile with no crystals. He has dactylitis of the right third toe and nail pitting. X-ray shows periostitis and juxta-articular new bone formation. What is the most likely diagnosis?

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Correct answer: B — Psoriatic arthritis

Inflammatory arthritis with psoriasis, dactylitis (sausage digit), nail changes (pitting, onycholysis), and radiographic periostitis/new bone formation is psoriatic arthritis. It is seronegative (RF and anti-CCP negative). CASPAR criteria are used for classification. Treatment depends on domain: NSAIDs, csDMARDs (methotrexate), or bDMARDs (anti-TNF, IL-17 inhibitors).

Reference: GRAPPA – 2024 – PsA Treatment Guidelines; EULAR 2023