Dactylitis Useful in Risk Stratification for PsA

Patients with early psoriatic arthritis (PsA) who present with dactylitis may have a more severe disease phenotype, investigators reported recently in the Annals of Rheumatic Diseases.

The researchers recruited patients who met classification criteria for PsA (CASPAR) and were naïve to disease-modifying antirheumatic drugs (DMARDs). They recorded patients’ clinical outcomes and conducted ultrasonography (US) to assess grey scale (GS) and power Doppler (PD) synovitis, periarticular cortical bone erosions, and enthesitis. The presence or absence of dactylitis was recorded and used to separate patient groups.

Of 177 patients with PsA, those with dactylitis (81/177, 46%) had higher tender joint counts (p<0.01), swollen joint counts (SJC) (p<0.001), and C reactive protein (CRP) levels (p<0.01) than patients without dactylitic PsA, the authors reported. Dactylitis was more prevalent in toes (146/214, 68.2%) than fingers (68/214, 31.8%) and ‘hot’ dactylitis was significantly more prevalent than ‘cold’ (83.6% vs 16.4%). US synovitis and erosions were also much more prevalent in dactylitic PsA (p<0.001 and p<0.001, respectively) than among patients without dactylitis.

“Exclusion of dactylitis in dactylitic PsA confirmed significantly greater SJC (3 vs 1, p=0.002), US synovitis (GS ≥2: 20.6% vs 16.1%, p<0.001, or PD ≥1: 5.1% vs 3.3%, p<0.001) ,and erosions (1.1% vs 0.5% joints, p=0.008; 26.1% vs 12.8% patients, p=0.035%) than nondactylitic PsA,” the authors noted. Synovitis (GS ≥2 and/or PD ≥1) occurred among 53.7% of patients with dactylitic PsA but the team found no substantial differences for US enthesitis between the 2 cohorts.

“Dactylitis signifies a more severe disease phenotype independently associated with an increased disease burden with greater SJC, CRP, US-detected synovitis and bone erosions in DMARD-naive early PsA and may be a useful discriminator for early risk stratification,” the authors concluded.

—Rebecca Mashaw

Reference:
Dubash S, Alabas OA, Michelena X, et al. Dactylitis is an indicator of a more severe phenotype independently associated with greater SJC, CRP, ultrasound synovitis and erosive damage in DMARD-naive early psoriatic arthritis. Ann Rheum Dis. Published online first: December 10, 2021. doi: 10.1136/annrheumdis-2021-220964