Psoriatic Enthesitis: An Update from the GRAPPA 2013 Annual Meeting

Abstract

The enthesis, attachment site of ligaments, tendons, and joint capsules to bone, has emerged as a complex structure or entheseal organ that dissipates stress to maintain homeostasis. Entheses are also anatomically and functionally integrated with adjacent bursa, fibrocartilage, and synovium in a synovial entheseal complex that may trigger inflammation in response to biomechanical stress. Recent studies have suggested that inflammation in psoriatic arthritis (PsA) arises in the enthesis based on imaging and anatomical data. In this review, the anatomy of the enthesis from a functional perspective is discussed, and the data that support a central role for enthesitis in PsA are outlined. In addition, new animal models that implicate Th17 and tumor necrosis factor pathways in enthesitis are highlighted along with new data that question the primacy of the enthesis in the early stages of PsA. Finally, future studies that incorporate new technologies are outlined. Those studies may address the contribution of entheseal inflammation to initiation and perpetuation of key pathophysiologic pathways in the psoriatic joint.

High-resolution MRI assessment of dactylitis in psoriatic arthritis shows flexor tendon pulley and sheath-related enthesitis

“…This region has been dubbed as a ‘functional’ enthesis unit, where the friction of the extensor tendon enthesis against the bone appears to be related to inflammation. 11 An epicentre of inflammation within this structure, rather than primarily within the synovium, offers a novel explanation for some of the extracapsular inflammatory change evident in dactylitis. It has been proposed that PsA is due to microtrauma, or ‘deep Koebner’ phenomenon, as recognised in skin psoriasis, 17 an observation that has been supported by animal model data.…”

“… 8 We have also noted ‘functional entheses’ disease at the extensor tendon and ligament enthesitis of the distal IP joint on cases of dactylitis on hrMRI, 9 10 where tendons and ligaments wrap around bony pulleys and are associated with fibrocartilage that reduces compression and shear. 11 The present study used hrMRI to explore the basis for PsA dactylitis by looking at the entheses and functional entheses-related structures. Given the dactylitis link with flexor tenosynovitis, we looked at the small entheses or flexor tendon pulleys that are sites of high mechanical stress and that have thus far not been explored as potential enthesis-related drivers of dactylitis.…”

Nail psoriasis as a predictor of the development of psoriatic arthritis

“…This hypothesis defines the occurrence of a common Koebnerization phenomenon ---the appearance of lesions at previous sites of microdamage and trauma ---and ultimately, inflammatory changes resulting from this stress could be responsible for the development of both nail disease and PsA joint changes. 4,29 This concept of joint Koebnerization can ultimately be considered an aberrant response to mechanical stress. 4,25,30 The link between psoriasis and HLA-Cw6 is well established, the latter representing the strongest genetic risk factor for the development of psoriasis.…”

Management of particular clinical situations in psoriatic arthritis: an expert’s recommendation document based on systematic literature review and extended Delphi process

“…When evaluating enthesitis, it is important to bear in mind the “enthesis organ”. It comprises the insertion of tendon and ligament to bone, but also adjacent tendon, bone fibrocartilage, fat pad, bursa, and synovium [ 105 ]. Therefore, clinical symptoms might be referred to any components of this complex and mechanical conditions, like fasciitis or bursitis, should be ruled out.…”