2. Immunologic factors
The inflammatory joint disease in psoriatic arthritis is led by immunologic factors. Different inflammatory cytokines are elevated in these patients, including IL-6, IL-1, and IL-8 in the synovial fluid and TNF-alpha in the blood. In this regard, the disease is similar to rheumatoid arthritis. The immunologic cause is probably related to activation of inflammation mediated by T helper 17 cells.