Psoriatic arthritis and ankylosing spondylitis may co-exist. Although psoriatic arthritis and ankylosing spondylitis are two different diseases, both are spondyloarthritis and can usually co-exist. Spondyloarthritis, which used to be called seronegative spondyloarthropathies, is a general term for a group of chronic inflammatory rheumatic diseases that primarily involve the spine, joint ligaments and tendons. The most typical disease is ankylosing spondylitis, but also includes reactive arthritis, psoriatic arthritis, inflammatory bowel disease arthritis, juvenile spondyloarthritis and undifferentiated spondyloarthritis. The onset of psoriatic arthritis may be related to genetic, immune and environmental factors, and its pathological changes are chronic synovitis with focal or diffuse inflammatory cell infiltration, which may be manifested as swelling and pain in the affected joints, limitation of movement, and joint deformity in severe cases, accompanied by psoriatic lesions with scaly erythema and other distributions in various parts of the body. Ankylosing spondylitis has a genetic predisposition, highly correlated with HLA-B27, chronic onset of disease, no obvious triggering factors, often manifested as the body’s central axis joints involved, such as sacroiliac joint lesions, typically manifested as spinal dendritic degeneration, the clinical manifestations of lower back pain with morning stiffness, lumbar spine activity is limited, HLA-B27 test is positive, the skin is usually no abnormal manifestations. Since both are spondyloarthritis, there is a possibility of coexistence. It is recommended that patients with psoriatic arthritis and ankylosing spondylitis go to the hospital in time and follow the doctor’s instructions for standardized treatment.