Dactylitis in psoriatic arthritis: prevalence and response to therapy in the biologic era

To determine the prevalence of acute dactylitis in patients with psoriatic arthritis (PsA) and to compare the response of new acute dactylitis to treatment with traditional disease-modifying antirheumatic drug (DMARD) and anti-tumor necrosis factor-α (anti-TNF) agents in a longitudinal PsA cohort.

Patients with PsA followed at 6 months according to a standard protocol from January 2000 to January 2010 were included in our study. Acute dactylitis was defined as the presence of painful swelling of an entire digit. Response was defined as either complete resolution of dactylitis or > 50% improvement in the number of dactylitic digits. A multivariate generalized estimating equations analysis using a negative binomial model to account for repeated measures was conducted to determine predictors for response to treatment of dactylitis.

Of the 752 patients seen in the clinic during this period, 294 had dactylitis in at least 1 visit, giving a prevalence of 39%. Patients with acute dactylitis and data available for response at 6 and 12 months (n = 252; 34% women, mean age 47 yrs, PsA duration 11 yrs) were included in the study on predictors of response to treatment. Multivariate analysis showed that treatment with anti-TNF agents was a significant predictor of improvement in dactylitis at 12 months (relative risk 0.528, 95% CI 0.283-0.985, p = 0.045).

The prevalence of dactylitis on at least 1 visit was 39%. Treatment was associated with improvement of dactylitis. Patients treated with biologics had better response to treatment compared with those treated with nonbiologic DMARD alone.