Background/Purpose: Enthesites and dactylitis are common phenomena in patients with psoriatic arthritis (PsA). Inspite of significant advances in our understanding of PsA pathophysiology in recent years, the structural changes underlying dactylitis in PsA have not been comprehensively assessed. Moreover, it is unknown which components of dactylitis respond best to immunosuppressive therapy. We therefore aim to employ most recently developed small joint MRI coils to generate high-resolution images of the fingers in PsA patients in order to analyse the contribution of the various inflammatory dactylitis lesions of PsA and analysing the responsiveness of these components to immunosuppressive therapy with highly active anti-TNF therapy.

Methods:   High resolution MRI scans (3 Tesla) with use of small joint coils of the clinical dominate hand were performed before and 6 months after switch from DMARD to anti-TNF therapy in 12 PsA patients with dactylitis (age 42 ± 18; disease duration 4 ± 3.3 years).

Results:   The following sites were most commonly involved in dactylitis: collateral ligament enthesitis 11/12 (92%); extensor tendons enthesitis 5/12 (42%); flexor tenosynovitis 9/12 (75%), periarticulitis (i.e. contrast enhancement in periarticular soft tissue) 9/12 (75%).After 6 months, periarticulitis was improved in 8/9 cases (89%), while residual enthesits at any site persisted in 6/11 patients (55%).

Conclusion: Dactylitis is a digital polyenthesitis with collateral ligaments and the extensor ligaments most frequently involved. Moreover periarticular contrast enhancement as well as tenosynovitis is regularly seen. Periarticulitis responds more readily to TNF-therapy than enthesitis. High-resolution MRI is a valid tool to investigate and monitor pathological findings in dactylitis in PsA patients.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/analysis-of-anatomical-sites-causing-dactylitis-and-their-responsiveness-to-change-under-tnf-therapy-in-psoriatic-arthritis-by-high-resolution-mri/