Ankylosing spondylitis (AS) is a systemic inflammatory disease that mainly invades the sacroiliac joints and spine, and can involve peripheral joints and visceral systems to varying degrees. In the early days, the disease was considered to be a special type of rheumatoid arthritis, called rheumatoid spondylitis, deforming spondylitis, rheumatoid central type, etc., and is now collectively referred to as ankylosing spondylitis. The characteristic pathological changes of AS are lesions of tendons, ligaments, and bone attachment points, with ligament calcification and bony ankylosis as its important characteristics. This disease is generally rheumatoid factor negative, and is classified as a seronegative spondyloarthropathy along with psoriatic arthritis, reactive arthritis, inflammatory bowel disease arthritis, undifferentiated spondyloarthropathy, etc.