Dactylitis signals greater disease burden in early psoriatic arthritis
Dactylitis indicates a more severe disease phenotype independently linked to increased disease burden, with greater bone erosion, in early DMARD-naïve psoriatic arthritis, according to data published in the Annals of the Rheumatic Diseases.
“The presence or history of dactylitis adds high sensitivity and specificity towards classifying PsA (CASPAR criteria),” Sayam R. Dubash, FRCP, MBChB, of the University of Leeds, in the United Kingdom, and colleagues wrote. “Further, dactylitis is associated with greater radiographic damage in chronic established PsA. However, to our knowledge, direct evaluation of the impact of dactylitis on overall disease phenotype and severity in early, untreated PsA has not been characterized.”
To analyze the impact of dactylitis on early PsA in patients who have not been treated with DMARDs, Dubash and colleagues recruited 177 such individuals into the Leeds Spondyloarthropathy Register for Research and Observation. Participants were classified by the presence or absence of dactylitis at baseline.
Among the participants, 81 had dactylitis. Clinical examinations included tender and swollen joint count, with ultrasonography used to analyze grey scale and power Doppler synovitis, periarticular cortical bone erosions and enthesitis. Ultrasound examinations were conducted by experienced, blinded ultrasonographers at 50 joints per patient.
According to the researchers, participants with dactylitis demonstrated higher tender joint counts (P < .01), swollen joint counts (P < .001) and C-reactive protein (P < .01), compared with those who were non-dactylitic. In addition, dactylitis was more prevalent in toes than fingers — 68.2% versus 31.8% — and tender, or “hot,” dactylitis was more prevalent than non-tender, or “cold,” dactylitis — 83.6% versus 16.4%. Synovitis (P < .001) and erosions (P < .001), as measured by ultrasound, were also significantly more prevalent in patients with dactylitis.
The researchers additionally found that excluding dactylitis in patients who were dactylitic confirmed significantly greater swollen joint counts — 3 versus 1 (P = .002) — ultrasound synovitis — for grey scale, at 20.6% versus 16.1% (P < .001), and power Doppler, at 5.1% versus 3.3% (P < .001) — and erosions — 1.1% versus 0.5% joints (P = .008) and 26.1% versus 12.8% patients (P = .035%) — compared with non-dactylitic PsA. Synovitis occurred in 53.7% of patients with dactylitis. There were no substantial differences for ultrasound enthesitis.
“The presence of dactylitis is independently associated with an increased burden of disease with greater [swollen joint count], [C-reactive protein], [ultrasound]-detected synovitis and erosive bone damage in DMARD-naïve early PsA,” Dubash and colleagues wrote. “Dactylitis should therefore be considered a clinical marker for a more severe phenotype in early PsA and may be an important discriminator for risk stratification in early intervention strategies.”