Clinical features of psoriatic arthritis
In most people with psoriatic arthritis, the arthropathy affects peripheral joints alone and may present with dactylitis (inflammation of a single finger or toe) or enthesitis (inflammation at the sites of tendon and ligament attachment to bone). The following patterns of joint involvement are recognised:
- oligoarticular peripheral arthritis—occurs in 50% of people; involves up to 5 joints. Over time many people with an initial oligoarticular presentation develop polyarticular disease
- polyarticular peripheral arthritis—occurs in 30% of people; may resemble rheumatoid arthritis
- predominant sacroiliitis (inflammation of the sacroiliac joints) and spondylitis (inflammation of the spine)—occurs in up to 10% of people. The sacroiliitis is usually asymmetrical. On plain X-ray the syndesmophytes are typically ‘chunky’, often with noncontiguous involvement of vertebrae
- predominant distal-interphalangeal joint involvement in both hands and feet—occurs in 5% of people. The distal interphalangeal joints involved are usually associated with severe psoriatic nail involvement
- arthritis mutilans—occurs in up to 5% of people. It presents as osteolysis or dissolution of bone affecting the small joints of the hands and feet and adjacent phalanges, resulting in shortening of digits and flail joints. This pattern is more commonly seen in females.
The extra-articular features common to spondyloarthritis may occur with psoriatic arthritis. Ocular inflammation most commonly presents as conjunctivitis, although up to 7% of people can develop acute anterior uveitis.
Markers of poor prognosis in psoriatic arthritis are:
- onset in childhood or as a young adult
- extensive psoriatic skin disease
- failure to respond to nonsteroidal anti-inflammatory drugs (NSAIDs)
- polyarticular presentation.