Enteropathic arthritis — SCE Rheumatology MCQ

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EasySpondyloarthropathiesEnteropathic arthritisSCE Rheumatology

A 38-year-old woman with Crohn disease develops atraumatic swelling of the right knee and left ankle during a flare of her bowel disease. She also has tenderness at both Achilles tendon insertions. Rheumatoid factor is negative and CRP is 86 mg/L. Knee aspiration yields inflammatory synovial fluid with no crystals, and Gram stain and culture are negative. What is the most likely diagnosis?

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Correct answer: C — IBD-associated peripheral spondyloarthritis

The correct answer is **IBD-associated peripheral spondyloarthritis**. The discriminating pattern is asymmetric lower-limb oligoarthritis accompanied by Achilles enthesitis in a patient with active Crohn disease. Peripheral enteropathic arthritis commonly parallels intestinal activity, unlike associated axial disease, which may follow an independent course. Negative rheumatoid factor is compatible with the seronegative spondyloarthritis spectrum. Septic arthritis must be considered with any acute swollen joint, but the multifocal pattern, enthesitis and negative culture argue against it. Absence of synovial crystals excludes CPPD, which would also be unusual at age 38. Rheumatoid arthritis more typically causes persistent symmetric small-joint polyarthritis, while sarcoid arthropathy would require supporting features such as erythema nodosum, ankle-predominant periarthritis or thoracic lymphadenopathy.

Reference: National Institute for Health and Care Excellence. NG65, Spondyloarthritis in over 16s: diagnosis and management, sections 1.1–1.2 and Context. 2017; last reviewed 4 March 2025. https://www.nice.org.uk/guidance/ng65/chapter/Recommendations