We found significantly higher levels of IL-22 in SF of PsA (17.75 ± 3.46 pg/ml) and RA (21.06 ± 3.55 pg/ml) compared to that in serum of PsA (9.22 ± 0.54 pg/ml) and RA (9.64 ± 1.20 pg/ml) (p < 0.01, Mann Whitney test). The gene discussed is IL22; the disease is rheumatoid arthritis.