Ankylosing spondylitis is a disease in which inflammation of the sacroiliac joints and spinal attachment points is the main symptom. There is a strong association with HLA-B27. Certain microorganisms (e.g. Klebsiella) have common antigens with the susceptible person’s own tissue and can trigger an abnormal immune response. It is a chronic inflammatory disease characterized by fibrosis and ossification of the large joints of the extremities, as well as the intervertebral disc rings and adjacent connective tissue, and joint ankylosis. Ankylosing spondylitis belongs to the category of rheumatic diseases and is a type of seronegative spondyloarthropathy. It is a chronic disease with the spine as the main lesion site, involving the sacroiliac joints, causing spinal ankylosis and fibrosis, resulting in varying degrees of eye, lung, muscle, and bone lesions, and is an autoimmune disease.