Psoriatic Arthritis

Psoriatic Arthritis

CR – Macrodactyly of the 3rd and 4th digits with hypertrophic interphalangeal degenerative and metacarpophalageal erosive changes.

Arthritis occurs in 5% of patients with psoriasis. Most often the arthritis symptoms develop years after skin disease but can antedate or occur simultaneously with psoriatic skin lesions. Enthesopathy, dactylics, synovitis (preferential involvement of flexor tendons), conjunctivitis and uveitis are common. ESR, IgA, uric acid, and c-reactive protein are often elevated. Rheumatoid factor is negative (i.e., seronegative). Synovial fluid is inflammatory with high leukocytes. Psoriatic arthritis tends to occur in a ray distribution, most pronounced distally but involving multiple joints. Erosions occur in the bare areas of joints but also the tufts and at tendon insertions; periarticular erosions have the mouse ear appearance in contrast to gull wing seen in erosive osteoarthritis. Severe erosions lead to the “pencil in cup” deformity. Periostitis in psoriatic arthropathy is poorly defined and irregular. The so called “sausage digit” is likely related to tenosynovitis, periostitis, and hyperemic overgrowth in children. Joint deformity related to flexion or medial/lateral deviation, arthritis mutilans (severe joint destruction), and ankylosis.

Martel W, Stuck KJ, Dworin AM, et al. Erosive Osteoarthritis and psoriatic arthritis: A radiologic comparison in the hand, wrist and foot. AJR (1980); 134:126-135.