Psoriatic Arthritis — SCE Rheumatology MCQ

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EasySpondyloarthropathyPsoriatic ArthritisSCE Rheumatology

A 33-year-old man presents with a right knee effusion, inflammatory low back stiffness and diffuse swelling of the entire left third toe. Examination shows nail pitting but no cutaneous psoriasis. Rheumatoid factor and anti-CCP antibodies are negative, and there has been no preceding gastrointestinal or genitourinary infection. What is the most likely diagnosis?

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Correct answer: E — Psoriatic arthritis

The diagnosis is psoriatic arthritis. Dactylitis, asymmetric peripheral arthritis, inflammatory axial symptoms and psoriatic nail dystrophy form a characteristic pattern, even without cutaneous psoriasis. Given established inflammatory musculoskeletal disease, nail dystrophy, current dactylitis and negative rheumatoid factor provide three CASPAR points. CASPAR criteria support, but do not replace, clinical diagnosis. Reactive arthritis can cause dactylitis and axial symptoms, but is less likely without a preceding gastrointestinal or genitourinary infection and does not explain psoriatic nail pitting. Rheumatoid arthritis usually causes symmetric peripheral synovitis; dactylitis and lumbar axial disease are atypical. Gout does not account for the chronic axial and nail features, while sarcoid arthropathy more often presents with ankle periarthritis and other features of sarcoidosis.

Reference: National Institute for Health and Care Excellence. Spondyloarthritis in over 16s: diagnosis and management (NG65), recommendations 1.1.2 and 1.2.1, 2017. https://www.nice.org.uk/guidance/NG65/chapter/Recommendations