2 Clinical need and practice
2.1 Psoriatic arthritis is an inflammatory arthritis affecting the joints and connective tissue and is associated with psoriasis of the skin or nails. The prevalence of psoriasis in the general population is estimated at 2–3%. The prevalence of inflammatory arthritis in people with psoriasis is estimated at up to 30%. At least 20% of people with psoriasis have severe psoriatic arthritis with progressive joint lesions. Psoriatic arthritis is a progressive disorder ranging from mild synovitis to severe progressive erosive arthropathy. People with psoriatic arthritis presenting with oligoarticular disease progress to polyarticular disease and a large percentage develop joint lesions and deformities, which progress over time. Despite clinical improvement with current DMARD treatment, joint damage has been shown radiologically in up to 47% of people with psoriatic arthritis at a median interval of 2 years.
2.2 Psoriatic arthritis can affect people's ability to work and carry out daily activities, which can have a substantial impact on quality of life. The impact of severe psoriasis on health-related quality of life is considered to be similar to that of other major medical conditions including diabetes, heart disease and cancer. People with psoriatic arthritis have a higher self-rated disease severity than those with psoriasis only. People with psoriatic arthritis have a 60% higher risk of mortality than the general population and their life expectancy is estimated to be approximately 3 years shorter.
2.3 Most people with psoriatic arthritis develop skin symptoms before joint symptoms, although joint symptoms may appear first or simultaneously. Psoriatic arthritis usually develops within 10 years of a diagnosis of psoriasis. The rheumatic characteristics of psoriatic arthritis include joint stiffness, pain and swelling, and tenderness of the joints and surrounding ligaments and tendons. Symptoms can range from mild to very severe.
2.4 Assessing the effectiveness of treatments for psoriatic arthritis relies on outcome measures that accurately and sensitively measure disease activity. Outcomes of effectiveness are based on measures of the anti-inflammatory response (such as the PsARC, and the American College of Rheumatology response criteria [ACR 20/50/70]), measures of psoriatic skin lesions (PASI), functional measures (Health Assessment Questionnaire [HAQ]) and radiological assessments (Total Sharp Score, van der Heijde-Sharp Score) of disease progression, quality of life and overall global assessments. Overall response criteria have not yet been clearly defined.
2.5 The aim of psoriatic arthritis treatment is to relieve symptoms, slow disease progression and maintain quality of life. To effectively manage psoriatic arthritis, any associated skin disease also needs to be effectively treated. Non-steroidal anti-inflammatory drugs (NSAIDs) and local corticosteroid injections are widely used. Disease that is unresponsive to NSAIDs, in particular polyarticular disease, is treated with DMARDs (currently, methotrexate and sulfasalazine are considered the DMARDs of choice) to reduce joint damage and prevent disability. Aggressive treatment of early stage progressive psoriatic arthritis can help to improve prognosis.