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The biomechanical link between skin and joint disease in psoriasis and psoriatic arthritis: what every dermatologist needs to know
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  1. Dennis McGonagle1,
  2. Ai Lyn Tan2,
  3. Michael Benjamin3
  1. 1
    Regeneative Medicine Institute, National University of Ireland, Galway, Ireland
  2. 2
    Academic Unit of Musculoskeletal Disease, University of Leeds and Chapel Allerton Hospital, Leeds, UK
  3. 3
    School of Biosciences, Cardiff University, Cardiff, UK
  1. Prof. Dennis McGonagle, Academic Unit of Musculoskeletal Disease, Chapel Allerton Hospital, Chapeltown Road, Leeds LS7 4SA, UK; d.g.mcgonagle{at}leeds.ac.uk

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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).1 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.

WHAT ULTRASOUND SHOWED IN ASYMPTOMATIC ENTHESES IN PSORIASIS

In the study, the authors used an ultrasound-based approach to examine five asymptomatic entheses in the region of the knee and heel (insertion of the quadriceps tendon, both ends of the patellar ligament, the insertion of the Achilles tendon and the calcaneal attachment of the plantar aponeurosis) in subjects with psoriasis, using the previously reported system from the Glasgow group: the Glasgow Ultrasound Enthesitis Scoring System (GUESS).2 An enthesis is composed of both soft tissue components (ligament, tendon and their associated fibrocartilages) and hard tissue components (calcified fibrocartilage, immediately adjacent bone (the “subchondral bone plate”) and the underlying trabecular network).3 While magnetic resonance imaging (MRI) is well suited to depicting the adjacent osteitis that may accompany enthesitis, ultrasound is probably the imaging …

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Footnotes

  • Competing interests: None declared

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