Psoriatic arthritis.

Psoriatic arthritis exhibits specific characteristics that create challenges for physicians attempting to manage the disease. Active research has produced new knowledge in the fields of epidemiology, diagnostic criteria, evaluation tools, outcome prediction, and treatment. Biotherapies have been introduced for psoriatic arthritis, creating a need for a reappraisal of evaluation tools, outcome prediction, and parameters reflecting treatment effects. TNF-alpha antagonists constitute a breakthrough in the management of psoriatic arthritis. Similar to rheumatoid arthritis and ankylosing spondylitis, psoriatic arthritis is entering a new era of evaluation and treatment.