Dermatology Book

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Psoriatic Arthritis

Aka: Psoriatic Arthritis
  1. See Also
    1. Psoriasis
  2. Epidemiology
    1. Incidence: Affects 7-20% of Psoriasis patients
    2. No gender predominance
    3. Onset at 12 years on average from the onset of psoriatic skin lesions
  3. Pathophysiology
    1. Spondyloarthropathy
    2. Seronegative inflammatory Arthritis
  4. Types
    1. Distal Interphalangeal Arthritis (Classic, 5% of cases)
      1. Adjacent nails may show psoriatic change
      2. Progressive bony erosions occur
    2. Arthritis mutilans (1-5% of cases)
      1. Severe osteolysis
        1. Phalanges
        2. Metatarsals
        3. Metacarpals
      2. "Opera glass" Digit
        1. Telescoping of skin over resorbed joint
    3. Symmetric Polyarthritis (15-25%)
      1. Rheumatoid Arthritis similarities
        1. Prominent Metacarpal disease
        2. Prominent proximal interphalangeal joint disease
      2. Rheumatoid Arthritis differences
        1. Milder course than Rheumatoid Arthritis
        2. No Extra-articular Rheumatoid Arthritis signs
          1. No Subcutaneous Nodules
          2. No Vasculitis
          3. No pulmonary involvement
        3. Rheumatoid Factor Seronegative
    4. Oligoarthritis (>50-70% of cases)
      1. Asymmetric joint involvement (<4 joints)
      2. Often presents as Arthritis in one knee
    5. Psoriatic Spondylitis
      1. Ankylosing Spondylitis type spine involvement
      2. Less associated with HLA-B27
      3. Atypical axial skeleton involvement
      4. Lumbar Spine most commonly affected
      5. Sacroiliitis (30%)
  5. Signs
    1. See above for signs specific to various Arthritis forms
    2. Careful skin exam for Psoriasis is imperative
    3. Inflammatory Arthritis
      1. Asymmetric distal joint involvement
      2. Joint Pain and tenderness to palpation
      3. Peripheral joint and spine stiffness
        1. Occurs >30 minutes in morning and after inactivity
    4. Skin lesions consistent with Psoriasis (60-80%)
      1. Arthritis may precede psoriatic dermatitis (20%)
      2. Classic psoriatic Plaques (See Psoriasis)
        1. Look at typical sites on extensor knee and elbow
        2. Examine scalp, ears, perineum, Umbilicus
      3. Nail Pitting or Onycholysis (See Psoriasis)
    5. Other Skin changes: Keratoderma blennorrhagica
      1. Hyperkeratotic Papules on plantar foot surface
      2. Also seen in Reactive Arthritis (Reiter's Disease)
    6. Sausage-shaped fingers and toes
      1. Also seen in Reactive Arthritis (Reiter's Disease)
    7. Enthesitis (ligament, tendon insertion inflammation)
      1. Also seen in Reactive Arthritis (Reiter's Disease)
      2. Achilles Tendonitis
      3. Plantar Fasciitis
      4. Patellofemoral Syndrome
    8. Other musculoskeletal involvement
      1. Sternoclavicular joint involvement
      2. Temporomandibular Joint involvement
    9. Ophthalmic changes
      1. Uveitis
  6. Differential Diagnosis
    1. Reactive Arthritis (Reiter's Disease)
    2. Ankylosing Spondylitis
    3. Rheumatoid Arthritis
    4. Septic Arthritis
    5. Gouty Arthritis (Seen in Psoriasis)
    6. HIV Infection (Cause of severe Psoriasis)
    7. Colitic Arthritis
  7. Diagnosis: Classification Criteria
    1. Major criteria (must be present)
      1. Established articular disease
    2. Minor Criteria (3 points or more present)
      1. Psoriasis
        1. Psoriasis currently active (2 points)
        2. Psoriasis history in past (1 point)
        3. Psoriasis in a first or second degree relative (1 point)
        4. Rheumatoid Factor negative (1 point)
        5. Psoriatic Nail Dystrophy (1 point)
      2. Dactylitis
        1. Entire digit currently swollen (1 point)
        2. Dactylitis history as diagnosed previously by a rheumatologist (1 point)
        3. Hand or foot XRay with new bone formation (not osteophytes) near joint margins (1 point)
    3. References
      1. Taylor (2006) Arthritis Rheum 54(8): 2665-73 [PubMed]
  8. Labs
    1. Rheumatoid Factor (RF) negative
    2. Erythrocyte Sedimentation Rate (ESR) increased
    3. Complete Blood Count (CBC)
      1. Mild normocytic normochromic Anemia
    4. Uric Acid elevated (Hyperuricemia) in severe Psoriasis
    5. Synovial Fluid Exam
      1. Synovial Fluid WBC 2,000 to 15,000 per mm3
      2. High Synovial Fluid WBC count seen in large effusions
    6. Serum Hemolytic complement elevated
    7. Serum electrophoresis
      1. Hypergammaglobulinemia
  9. Imaging
    1. XRay of involved joints
      1. Bony erosions
      2. Pencil-in-a-cup deformity at DIP joints
        1. Whittling of proximal phalanx
        2. Expanded base of distal phalanx
    2. Spine XRay (Cervical, Thoracic or Lumbar)
      1. Unilateral asymmetric syndesmophytes in skip pattern
      2. Bamboo spine of Ankylosing Spondylitis rarely occurs
      3. Asymmetric Sacroiliitis
      4. Asymmetric paravertebral ossification
  10. Management
    1. Treat underlying Psoriasis
    2. Physical Therapy
      1. Learn to protect affected joints
      2. Perform strengthening and range of motion Exercises
    3. NSAIDs in mild cases
    4. Consider Corticosteroids
      1. Intra-articular Corticosteroid
      2. Systemic Corticosteroid
    5. Disease modifying agents in moderate to severe cases
      1. TNF-a inhibitor
        1. Adalimumab (Humira)
        2. Etanercept (Enbrel)
        3. Infliximab (Remicade)
        4. Ustekinumab (Stelara)
      2. Sulfasalazine (Azulfidine)
      3. Methotrexate (avoid in HIV Infection)
      4. Cyclosporine (avoid in HIV Infection)
      5. Azathioprine (Imuran) (avoid in HIV Infection)
      6. Gold Salts
      7. Penicillamine
  11. References
    1. Klippel (1997) Primer Rheumatic Diseases, p. 175-9
    2. Bennett (2004) Radiol Clin North Am 42:121-34 [PubMed]
    3. Bulbul (1995) Postgrad Med 97(4):97-106 [PubMed]
    4. Kataria (2004) Am Fam Physician 69:2853-60 [PubMed]
    5. Mease (2003) Rheum Dis Clin North Am 29:495-511 [PubMed]
    6. Weigle (2013) Am Fam Physician 87(9): 626-33 [PubMed]

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