Psoriatic Dactylitis: Current Perspectives and New Insights in Ultrasonography and Magnetic Resonance Imaging

Abstract

Dactylitis, one of the most typical features of psoriatic arthritis (PsA), is the diffuse swelling of the digits and is determined by the involvement of different anatomic structures, including: the subcutaneous fibrous tissue "accessory pulley" system; flexor tendons, with their related structures; the articular synovium; the small enthesis of the hands. Dactylitis is currently considered both a marker of disease activity and severe prognosis and its importance in PsA is emphasized by the inclusion in the classification criteria of PsA. This review focuses on the role of imaging in the management of PsA patients with dactylitis in clinical practice and in a research setting. Furthermore, imaging could be a valuable tool to assist in unravelling some of the underlying mechanisms of the onset and chronicization of dactylitis in PsA patients.

Keywords: dactylitis; imaging; psoriatic arthritis; score; ultrasound.

Figure 1

Photograph of hand dactylitis: The first finger of the right hand is affected by dactylitis. Image courtesy of Dr. Alen Zabotti.

Figure 2

This figure summarizes the clinical and ultrasound characteristics of acute/hot and chronic/cold forms of dactylitis: Flexor tenosynovitis and soft tissue oedema are predominant in early cases, whereas synovitis is more frequent in the chronic form. Similarly, local symptoms are linked with extracapsular lesions, particularly flexor tenosynovitis and soft tissue oedema; joint synovitis does not seem to correlate with pain.

Figure 3

Prevalence of some US abnormalities after splitting cases into quartiles based on dactylitis duration: US: ultrasound; GS: greyscale; PD: power Doppler; PDS: subcutaneous PD signal; PIP: proximal interphalangeal. Figure reproduced from the article: Girolimetto et al. J Rheumatol. February 2020;47(2):227–233.

Figure 4

Evolution of dactylitis. Inflammation initially compromises the extracapsular structures and subsequently extends to the joint structures. The US lesions underlying dactylitis change over time, like evolving from a chrysalis to a butterfly. In particular: a) in the early phase flexor tenosynovitis and soft tissue oedema are prevalent. Joint synovitis is often absent; b) in the intermediate phase, both flexor tenosynovitis and synovitis may be present; c) in the late-chronic phase, joint synovitis is prevalent while flexor tenosynovitis is often absent or present but of minimal degree.