Identification of Serum Level of Glutathione Peroxidase 4

Inclusion Criteria: * Patients diagnosed as ankylosing spondylitis according to ASAS criteria . \[13\] * Patients diagnosed as psoriatic arthritis according to CASPAR criteria. \[14\] * Age (\>18). Exclusion Criteria: * Patient with other autoimmune Rheumatic diseases. * patients with any of the following conditions: I) severe liver and kidney dysfunction; II) hematopoietic diseases; III) infectious diseases; IV) tumors; or V) other wasting diseases. \[15\] * patients received certain drugs (for example, sulfasalazine, artemisinin, statins), and experimental reagents (such as erastin) .\[16\]