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Rheumatology

Arthritis - Approach

  • First step to to determine extent of involvement: mono vs oligo vs polyarthritis
  • Monoarthritis:
    • Differential diagnosis
      • Trauma: hemarthrosis, fracture, ligamentous injury
      • Infection: staphylococcus, streptococcus, neisseria, GNRs, TB, fungal, Lyme
      • Crystal: gout, pseudogout
      • Rheumatologic: seronegative spondylarthropathy, sarcoid, RA, OA
    • History: assess timing, antecedent trauma, systemic complaints
    • Exam: presence of synovitis (warmth, swelling, effusion), indicates that inflammatory process is present
      • Septic and crystal arthritis have nearly identical clinical features, and can occur concomitantly
      • Fever, leukocytosis, ESR, and CRP are non-specific (see attached JAMA article)
    • Management: Given the difficulty in differentiating, aspiration should be performed in all joints with signs of inflammation
      • Aspiration: send cell count, GS, culture, crystals
        • Cell count:
          • >2K WBC/mm3 indicates inflammatory process
          • >50K WBC/mm3 suggests infection (+LR 7.7), with higher levels more strongly suggestive
            • However, this is not a clean dichotomy, and overlap exists
          • >90% PMNs also suggests infection (+LR 3.4)
      • Treatment:
        • Septic arthritis: joint should be drained urgently, then IV abx x 2 weeks, followed by PO
        • Pseudogout: intraarticular steroids and NSAIDs

 

(Christopher Woo MD, 11/1/10)