The biomechanical link between skin and joint disease in psoriasis and psoriatic arthritis: what every dermatologist needs to know.

INTRODUCTION In this issue of the Annals of the Rheumatic Diseases, Gisondi et al (see page 26) present an ultrasonography study showing that otherwise asymptomatic patients with psoriasis often have evidence for subclinical disease involving the enthesis (ie, the site of insertion of a tendon, ligament or joint capsule to bone). The authors suggest that this may represent a useful approach for the future prediction of which patients with psoriasis will eventually develop an associated arthropathy. While the value of such a strategy in otherwise healthy patients with a common disease such as psoriasis is debatable, it is clear that, if validated and reproduced, the present findings could have far reaching consequences for understanding the link between skin and joints in psoriasis. In particular it further challenges the concept that the primary link between skin and joint disease is related to common autoimmune mechanisms affecting the skin and synovial membrane. Given that entheses are sites of particularly high joint stressing, it further supports the alternative emerging view that the link could be a biomechanical one.