Psoriatic arthritis develops in fewer than 10% of patients with psoriasis. It is typically gradual in onset and patients usually have skin disease for months to years before arthritis develops. It is usually asymmetric and polyarticular. Smaller joints of the upper extremities are most commonly involved. Characteristic clinical signs include "sausage digits" and "pitted nails". Initial treatment is NSAIDS, but persistent arthritis may require methotrexate or anti-TNF agents.