Low dose cyclosporine A in psoriatic arthritis: relation between soluble interleukin 2 receptors and response to therapy.

Twelve patients with psoriatic arthritis (PsA) were treated with low doses of cyclosporine A (CsA) (the initial dose was 3 mg/kg daily) and were entered into an open 6-month study. At the end of the study arthritis was improved in 7 patients (number of patients achieving a 50% or more reduction in the number of swollen or tender joints) and unchanged in 4 patients. Cutaneous psoriasis also improved significantly as shown by psoriasis area and severity index score. Only one patient withdrew from the study after one month because of severe nephrotoxicity. Serum creatinine fell to baseline value 6 weeks after the discontinuation of CsA. Three patients had minor side effects. CsA maintained articular improvement also in the 9 patients who are still taking this drug (mean duration of therapy of 12 +/- 0.8 months). There was no significant reduction of erythrocyte sedimentation rate during the study period. We assayed levels of soluble interleukin 2 receptors (sIL-2R) in serial serum samples obtained from 10 patients during the study period. Concentrations of sIL-2R were significantly increased in patients with PsA compared to controls. In 6 responder patients we observed a parallel decrease in joint pain/tenderness score and serum sIL-2R values. This finding was not observed in 4 nonresponders. Our results suggest that low dose CsA is a short term effective and safe therapy in patients with PsA and that serial sIL-2R levels are a useful means of measuring changes in disease activity.