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Psoriatic arthritis is a chronic inflammatory arthritis that affects 5–42% of persons with psoriasis. Some pts, especially those with spondylitis, will carry the HLA-B27 histocompatibility antigen. Onset of psoriasis usually precedes development of joint disease; approximately 15–20% of pts develop arthritis prior to onset of skin disease. Nail changes are seen in 90% of pts with psoriatic arthritis.
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PATTERNS OF JOINT INVOLVEMENT
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There are five patterns of joint involvement in psoriatic arthritis.
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Asymmetric oligoarthritis: often involves distal interphalangeal/proximal interphalangeal (DIP/PIP) joints of hands and feet, knees, wrists, ankles; “sausage digits” may be present, reflecting tendon sheath inflammation.
Symmetric polyarthritis (40%): resembles rheumatoid arthritis except rheumatoid factor is negative, absence of rheumatoid nodules.
Predominantly DIP joint involvement (15%): high frequency of association with psoriatic nail changes.
“Arthritis mutilans” (3–5%): aggressive, destructive form of arthritis with severe joint deformities and bony dissolution.
Spondylitis and/or sacroiliitis: axial involvement is present in 20–40% of pts with psoriatic arthritis; may occur in absence of peripheral arthritis.
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Negative tests for rheumatoid factor.
Hypoproliferative anemia, elevated ESR.
Hyperuricemia may be present.
HIV infection should be suspected in fulminant disease.
Inflammatory synovial fluid and biopsy without specific findings.
Radiographic features include erosion at joint margin, bony ankylosis, tuft resorption of terminal phalanges, “pencil-in-cup” deformity (bone proliferation at base of distal phalanx with tapering of proximal phalanx), axial skeleton with asymmetric sacroiliitis, asymmetric nonmarginal syndesmophytes.
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TREATMENT: PSORIATIC ARTHRITIS