Reactive Arthritis

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Intro & Causes - The Trigger Tale

  • Reactive Arthritis (ReA): A seronegative spondyloarthropathy, an immune-mediated aseptic synovitis triggered by infection elsewhere.
  • Key Triggers:
    • Urogenital: Chlamydia trachomatis
    • Gastrointestinal: Salmonella, Shigella, Yersinia, Campylobacter spp.
    • 📌 Mnemonic (GI/GU): ShY ChiCS (Shigella, Yersinia, Chlamydia, Campylobacter, Salmonella)
  • Genetic Link: Strong HLA-B27 association (↑ susceptibility, often more severe disease).

⭐ Reactive arthritis is classically an aseptic synovitis occurring after an extra-articular infection. Gut Microbiome and Inflammation in Reactive Arthritisoka

Symptoms - Can't See, Can't Pee, Can't Climb a Tree

📌 Classic Triad: "Can't see, can't pee, can't climb a tree"

  • Arthritis: Asymmetric oligoarthritis (≤ 4 joints), predominantly lower limbs. (Can't Climb a Tree)
    • Dactylitis ("sausage digits"). Dactylitis (sausage digit) in reactive arthritis
    • Enthesitis (e.g., Achilles tendonitis, plantar fasciitis).
    • Sacroiliitis & inflammatory low back pain.
  • Urethritis/Cervicitis: Dysuria, discharge. (Can't Pee)
  • Conjunctivitis/Uveitis: Eye pain, redness. (Can't See)

Extra-articular Manifestations:

  • Skin: Keratoderma blenorrhagicum (palms/soles), circinate balanitis.
  • Nails: Onycholysis, subungual hyperkeratosis.
  • GI: Diarrhea (often preceding).
  • Cardiac (rare): Aortitis, conduction abnormalities.

⭐ Dactylitis ('sausage digit') is a characteristic feature of reactive arthritis and other spondyloarthropathies.

Diagnosis - Detective Work

Primarily a clinical diagnosis; no single pathognomonic test.

  • Laboratory Findings:

    • ↑ESR, ↑CRP (indicate inflammation).
    • HLA-B27: Positive in 30-50% of patients.
    • Synovial fluid: Inflammatory, culture-negative.
  • Imaging (X-rays):

    • Features: Erosions, joint space narrowing, periostitis ('fluffy').
    • Key sites: Sacroiliitis (often asymmetric), enthesophytes (e.g., heel).
  • Exclude Triggering Infections:

    • Stool and urine cultures.
    • Chlamydia PCR (if clinically suspected).

⭐ Synovial fluid analysis in reactive arthritis typically shows inflammatory changes (WBC 5,000-50,000/mm³) but is culture-negative.

Rule-Outs - Not That Arthritis!

ConditionKey Differentiator vs. ReA (Sterile, Asymmetric)
Septic ArthritisFever, monoarticular, purulent fluid, +Gram/culture
Gout/PseudogoutCrystals (urate/CPPD) in synovial fluid, acute monoarthritis
Psoriatic Arth.Psoriasis, nail pitting, dactylitis, DIP involvement
Ankylosing Spond.Predominantly axial (sacroiliitis), HLA-B27 >90%
Rheumatoid Arth.Symmetric polyarthritis (small joints), RF/Anti-CCP +ve

Treatment - Taming the Reaction

Goals: Relieve symptoms, eradicate active infection (if present), prevent chronic complications.

  • NSAIDs: First-line for acute arthritis and enthesitis, providing symptomatic relief.
  • Corticosteroids: Intra-articular or systemic for refractory symptoms unresponsive to NSAIDs.
  • DMARDs: Sulfasalazine, Methotrexate for chronic or severe disease to prevent progression.
  • Antibiotics: Only if active infection (e.g., Chlamydia) is proven; controversial for post-dysenteric ReA.

    ⭐ Antibiotics are generally not recommended for post-enteric reactive arthritis unless an active infection is proven.

  • Physiotherapy: Essential for maintaining joint function and muscle strength throughout.

Outlook & Issues - The Long Haul

  • Prognosis: Variable; often self-limiting (weeks/months). Chronic/recurrent in 15-30% of cases.
  • Complications:
    • Chronic arthritis, sacroiliitis, ankylosing spondylitis.
    • Recurrent uveitis.
    • Cardiac: conduction defects, aortic regurgitation.

⭐ A significant minority (15-30%) of patients with reactive arthritis may develop chronic or recurrent disease.

High‑Yield Points - ⚡ Biggest Takeaways

  • Reactive Arthritis: an aseptic inflammatory arthritis triggered by GI (Salmonella, Shigella, Yersinia) or GU (Chlamydia) infections.
  • Classic triad: "Can't see, can't pee, can't climb a tree" (conjunctivitis/uveitis, non-gonococcal urethritis, arthritis).
  • Strong association with HLA-B27 positivity.
  • Typically an asymmetrical oligoarthritis, predominantly affecting lower limb large joints.
  • Extra-articular features: enthesitis, dactylitis, keratoderma blenorrhagicum, circinate balanitis.
  • Synovial fluid: inflammatory, sterile (culture-negative).

Practice Questions: Reactive Arthritis

Test your understanding with these related questions

A patient presents with severe pain and swelling in his knee joint for 10 days. He also complains of pain and discomfort during urination. He says that he had diarrhea one month ago and he has been unwell since then. What is the most likely diagnosis?

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Flashcards: Reactive Arthritis

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_____ arthritis is associated with a 'pencil-in-cup' deformity on X-ray with subluxation of thumb

TAP TO REVEAL ANSWER

_____ arthritis is associated with a 'pencil-in-cup' deformity on X-ray with subluxation of thumb

Psoriatic

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