Psoriatic arthritis — SCE Rheumatology MCQ

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EasySpondyloarthropathiesPsoriatic arthritisSCE Rheumatology

A 45-year-old woman with established plaque psoriasis presents with a 6-week history of painful swelling of several finger joints and heel pain. Examination shows synovitis of two finger joints, dactylitis of the right second toe, tenderness at the Achilles tendon insertion and nail pitting. Rheumatoid factor and anti-CCP antibodies are negative, and CRP is 26 mg/L. What is the most likely diagnosis?

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Correct answer: A — Psoriatic arthritis

The diagnosis is psoriatic arthritis. The combination of established psoriasis, inflammatory peripheral synovitis, dactylitis, Achilles enthesitis and psoriatic nail pitting is highly characteristic. She also fulfils the feature-based CASPAR classification framework through current psoriasis, nail dystrophy, dactylitis and rheumatoid-factor negativity. Seronegative rheumatoid arthritis remains possible in a patient with psoriasis, but dactylitis, enthesitis and nail disease strongly favour psoriatic arthritis. Reactive arthritis may cause enthesitis and dactylitis, but there is no preceding gastrointestinal or genitourinary infection and the psoriatic phenotype is compelling. Gout usually causes episodic crystal arthritis, while erosive osteoarthritis does not explain Achilles enthesitis or dactylitis.

Reference: National Institute for Health and Care Excellence. NG65: Spondyloarthritis in over 16s: diagnosis and management, recognition and referral recommendations and context. 2017. https://www.nice.org.uk/guidance/NG65/chapter/Recommendations