Psoriatic arthritis is a chronic autoimmune inflammatory disease affecting peripheral joints entheses and axial sites along with skin and nails. Szentpetery A et. Al., analyzed the changes in immunohistochemical expression markers of synovial and skin inflammation, clinical outcomes and magnetic resonance imaging (MRI) scores with abatacept treatment in patients with psoriatic arthritis (PsA). 

This single-centered, crossover study, recruited 15 PsA patients with active disease including synovitis of a knee and naïve to biological-treatment. The patient randomly received intravenous abatacept 3 mg/kg of body weight or placebo infusion on day 1, 15 and 29. After this abatacept 10 mg/kg of body weight was administered every 28 days for 5 months and the data was collected during each visit. Synovial biopsy of the involved knee was obtained at baseline, 2 and 6 months. Before arthroscopy, MRI of the same knee and skin biopsy was also performed.

Significant improvements was seen in the joint-related measures, in which 90% were European League Against Rheumatism criteria responders and 30% achieved psoriasis area severity index (PASI) 50 at 6 months. Synovitis (P=0.016) and vascularity (P=0.039) macroscopic scores were found to decrease consistently with decrease in total MRI score (P=0.016). Abatacept brought a decrease in the immunohistological expression of FOXP3+ cells (P=0.027), mainly the expression of CD4+FOXP3+ regulatory T cells (Tregs) (P=0.008) in the synovium over 6 months. As such no significant clinical or immunohistological change in any of the skin measures was observed.