Psoriatic and reactive Arthritis

Psoriatic Arthritis

• Definition: A seronegative arthritis associated with psoriasis, often developing skin involvement within weeks to months.
• Epidemiology: Affects 10%-40% of psoriasis patients, equally common in males and females, typically between ages 25-40.
• Clinical Presentations:
  • Asymmetrical Mono/Oligoarthritis: Affects fingers and toes (dactylitis-sausage digits), large joints (knees, ankles) with potential for large effusions.
  • Symmetrical Polyarthritis: Similar to rheumatoid arthritis, appearing in 25% of cases, more common in females.
  • Psoriatic Spondylitis: Back pain and stiffness affecting any spinal structure.
  • Arthritis Mutilans: Finger deformities (telescoping fingers), in about 5% of cases.
  • Nail Changes: Pitting, onycholysis, subungual hyperkeratosis, and horizontal ridging (found in 85% of cases).
• Investigations & Diagnosis: Primarily clinical, elevated ESR & CRP, negative serology (low RF, ACPA, ANA). X-ray may show small bone sclerosis & marginal erosions (but may be normal).
• Treatment: Weight loss, NSAIDs, intra-articular glucocorticoids, DMARDs (especially methotrexate), anti-TNF-α (infliximab) for unresponsive cases, and monoclonal antibodies as needed.

Reactive Arthritis

• Definition: An inflammatory arthritis linked to a prior joint infection. Often includes Reiter's Syndrome (triad: arthritis, conjunctivitis, urethritis).
• Epidemiology: Most commonly sexually acquired (SARA), primarily affecting young males (15:1 male-to-female ratio), typically under 35 years.
• Causative Organisms: Salmonella, Shigella, Chlamydia, Campylobacter, Yersinia.
• Clinical Pictures:
  • Develops 2-4 weeks post-infection, lasting 2-4 months.
  • Asymmetrical Oligoarthritis: Primarily lower limbs.
  • Enthesitis: (Most prominent) Achilles tendonitis, plantar fasciitis.
  • Sacroiliitis: (15-20%) low back pain and stiffness. (First attack usually self-limiting, but recurrence/chronicity can develop). (10% have active disease 20 years later.)
  • Circinate Balanitis: Painless vesicles on the glans penis.
  • Conjunctivitis & Anterior Uveitis: (30% of chronic cases).
  • Painless Buccal Erosion: (mouth ulcers).
  • Urethritis: Dysuria, urine incontinence.
• Investigations & Diagnosis: Primarily clinical, elevated ESR & CRP, vaginal swab (to rule out Chlamydia if applicable), negative serology (RF, ACPA, ANA).
• Treatment: Rest, NSAIDs, intra-articular/systemic glucocorticoids, DMARDs for persistent symptoms, and if Chlamydia infection is present, a short course of doxycycline or single dose of azithromycin.