Psoriatic arthritis.

Psoriatic arthritis is a chronic inflammatory arthropathy that affects approximately 6% to 48% of patients with psoriasis. Arthritis is not correlated with the extent of skin disease. Classic radiographic findings of the involved joint include erosion, ankylosis, and fluffy periostitis. Site-specific characteristic deformities such as pencil-in-cup deformity of the phalanges also may be present. The disease typically follows a moderate course, but up to 47% of cases develop into destructive arthritis in which the inflammatory process leads to bony erosion and loss of joint architecture. The mainstay of treatment is biologic therapy (eg, tumor necrosis factor-α inhibitors) in conjunction with disease-modifying antirheumatic drugs. Patients with end-stage joint destruction may require surgery to alleviate pain and restore function. Orthopaedic surgeons should be cognizant of the risk factors (eg, increased risk of cardiovascular disease) and potential complications (eg, poor wound healing and increased risk of infection) associated with psoriatic arthritis.