Dactylitis in psoriatic arthritis: a marker for disease severity?

Aim: To describe dactylitis in a large cohort of patients with psoriatic arthritis followed prospectively in a specialist clinic, and identify whether it is associated with a worse prognosis. Methods: Between 1979 and 1999, 537 patients were registered in the psoriatic arthritis clinic and entered onto a longitudinal database. Patients were followed prospectively at six to 12 month intervals according to a standard protocol, and all information was entered onto a database. The database was searched for patients with dactylitis. Descriptive statistics were used to describe the population and chi(2) tests to relate dactylitis to radiographic changes. Results: Dactylitis was documented in 260 patients (48%); 69% of the episodes were recorded at presentation to the clinic. Dactylitis affected feet only in 65% of cases, hands only in 24%, and both hands and feet in 12%. Recurrent dactylitis occurred in 44% of the patients. Increased radiological progression was noted in digits showing dactylitis compared with those without dactylitis (50% v 38%, respectively; p<0.0001). Conclusions: Dactylitis is common among patients with psoriatic arthritis. It most often affects the feet, in an asymmetrical distribution. It is associated with a greater degree of radiological damage than occurs in digits not affected by dactylitis.