Diagnosis and management of psoriatic arthritis

Psoriatic arthritis (PsA) is considered to be one of the spondyloarthritides, and as such has both spinal and peripheral joint involvement. In 80% of patients, psoriasis usually precedes the development of arthritis. Although there are no widely accepted diagnostic criteria, a number of distinct clinical features allow it to be distinguished from other forms of inflammatory arthritis. It affects both sexes equally, and the pattern of joint involvement is characteristic with distal interphalangeal joint involvement, asymmetry, dactylitis, flail or ankylotic deformities of digits, and the frequent presence of enthesitis and spinal involvement. It may have a pattern of joint involvement similar to rheumatoid arthritis (RA) but in these patients rheumatoid factor and the other systemic features of RA are usually absent. Radiographs frequently reveal evidence of asymmetric sacroiliitis and spinal disease, and peripheral joints, as well as showing erosions, may also demonstrate profuse new bone formation and ankylosis. Profound osteolysis producing the pencil-in-cup deformity can also occur in the same individual. It is now recognised that PsA can be a destructive arthritis with an increased morbidity and mortality. Studies of standard disease-modifying therapies have been small and frequently inconclusive because of a high placebo response rate. This may be as a result of heterogeneity in patient selection, poor assessment tools, or the difference in underlying pathogenesis and subsequent response to therapy. In meta-analyses, sulfasalazine and methotrexate have been shown to be effective. Treating the skin alone seems to have little impact on joint disease, and the relationship between skin and joints is still unclear. However, recent studies with anti-tumour necrosis factor agents, such as etanercept and infliximab, have shown considerable significant clinical benefit and provided the hope that we will at last have effective therapies for this disease.