The preclinical phase of PsA: a challenge for the epidemiologist

Psoriatic arthritis (PsA) is a chronic inflammatory arthritis and, like many chronic diseases, often has an insidious onset. The disease likely begins well before patients first present to a rheumatologist and even before they first have symptoms. Several studies have confirmed the presence of subclinical joint and entheseal inflammation in patients with psoriasis.1–5 However, relatively little is known about the preclinical phase of PsA. The ‘preclinical phase’ is emerging as an important issue in many rheumatic diseases and is an important area of ongoing research. A preclinical phase in rheumatoid arthritis (RA) has been fairly well described. Current research suggests that, among predetermined or genetically susceptible individuals, an inciting agent (eg, smoking) ignites asymptomatic inflammation. This is followed by asymptomatic synovitis, development of symptoms, a transition to clinically apparent RA and subsequent diagnosis, and then a chronic inflammatory phase.