19th January 2024

Background

Definition

Psoriatic arthritis is a chronic seronegative inflammatory arthritis which affects joints and connective tissue and is associated with psoriasis of the skin or nails. Psoriatic arthritis can also affect tendons, leading to dactylitis (swelling of digits) or enthesitis. It is a progressive disorder, and the presentation can range from mild synovitis to the development of severe erosive arthropathy in around 40-60% of patients.

Epidemiology

Psoriatic arthritis has been shown to affect around 20-30% of patients with psoriasis and is more common in the middle-aged Caucasian population. It correlates poorly with skin psoriasis and can often precede the development of skin symptoms. Due to the clinical heterogeneity of symptoms and the absence of skin signs in some patients, the prevalence and incidence of psoriatic arthritis may be underreported. Males and females are equally affected; however, males tend to experience an earlier onset of disease.

Causes and risk factors

The aetiology of psoriatic arthritis is unknown; however, there appears to be an increased incidence of the disease in first-degree relatives. Risk factors include family history of psoriatic arthritis, presence of HLA-B27 genotype, obesity, smoking and psoriatic nail disease. Those patients who have sustained trauma to joints or tendons, or those with a history of infections, particularly HIV, are also at increased risk for the development of psoriatic arthropathy.