For scoring, the weights applied are 0–1 (i.e., 0 is not tender, 1 is tender) for the basic Leeds index, and 0–3 (i.e., 0 has no tenderness and 1–3 indicates increasingly higher degrees of tenderness) for the initial index. The Leeds index counts only acute dactylitis.
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Explore This IssueSeptember 2018
Dactylitis can also be demonstrated on ultrasound and MRI, as described above.
Multiple clinical and ultrasound enthesitis indices exist or are in development. Although clinical enthesitis indices are the most feasible to perform, they are also the most difficult to align with the true pathophysiological process underlying enthesitis because they rely on the assumption that tenderness to pressure is representative of PsA entheseal inflammation. Confounding factors for PsA enthesitis on clinical or imaging assessment include pain attributable to anatomical structures in proximity to entheses, degenerative processes, physiological enthesial complex aging and overuse/injury, among others.
Two comprehensive clinical enthesitis indices include the Spondyloarthritis Research Consortium of Canada enthesitis index (SPARCC) and the PsA modified Maastricht Ankylosing Spondylitis Enthesitis Score (MASES). Both have been used in PsA clinical trials. SPARCC assesses entheses that are predominantly peripheral by tenderness to standardized pressure applied on examination of 18 sites. The SPARCC score range is 0–16, and higher scores indicate more entheseal sites are tender.
Using the same examination technique, the PsA-modified MASES index assesses axial and lower extremity entheses at 15 sites with a score range of 0–15. Higher PsA modified MASES scores indicate more entheseal sites involved (see Figures 6A and 6B).
Imaging studies, particularly ultrasound, are more sensitive at detecting peripheral enthesitis than clinical exams, and they can identify subclinical entheseal involvement as well as characterize anatomical changes more specific to an inflammatory disease. Both inflammatory changes (e.g., tendon thickening and hypoechogenicity near insertion, bursitis, Doppler enhancement, etc.), as well as damage changes (e.g., bone erosions, enthesophytes, etc.) can be seen (see Figure 7).12
Dactylitis and enthesitis are both regarded as signs of PsA disease severity. Dactylitis is associated with joint erosions.14 Enthesitis is associated with worse disease and radiographic damage in psoriatic arthritis.9 Depending on location (e.g., the Achilles tendon), dactylitis can cause disability and adversely impact a patient’s life in addition to other PsA manifestations.
To date, no studies have been sufficiently powered to investigate the treatment of dactylitis and enthesitis, but several studies have reported them as secondary endpoints. The Group for Research and Assessment of Psoriasis and Psoriatic Arthritis (GRAPPA) and the European League Against Rheumatism (EULAR) recommend corticosteroid injections and conventional synthetic disease-modifying anti-rheumatic drugs (DMARDs) as first-line therapy for dactylitis, and NSAIDs and physiotherapy as first-line therapy for enthesitis. In patients who fail to respond, these steps are followed by biologics (e.g., TNF inhibitors).15,16