Ankylosing spondylitis is a disease characterized by chronic inflammation of the medial joints (sacroiliac joints and spine), which can also involve internal organs and other tissues. The course of the disease is chronic and progressive, with alternating episodes of exacerbation and remission. In typical cases, X-rays show marked destruction of the sacroiliac joints and “bamboo-like” changes in the spine in later stages. 90% of patients are HLA-B27 positive, while the rate of HLA-B27 positivity in the general population is only about 6%. The cause of the disease is not known, but is generally assumed to be due to the interaction of genetic and environmental factors. Inflammation occurs mainly in the synovial membrane and joint capsule, ligaments and tendon bone attachment points. There may also be iritis, aortic radiculitis, amyloidosis, and secondary fractures. The disease is mostly slow and insidious in onset and is easily misdiagnosed. It is more common in men, with a male-to-female ratio of about 5 to 10:1. Men generally have more severe symptoms than women. The age of onset is 10 to 40 years old, with a peak incidence at 20 to 30 years of age, and less frequently at 40 to 50 years of age or older. those with onset before 16 years of age are called juvenile ankylosing spondylitis. those with onset after 45 to 50 years of age are called late onset ankylosing spondylitis, and the clinical presentation is often atypical. Special reminder: When you have the following symptoms need to find a specialist to rule out the disease. 1, young people, with lumbosacral pain. There is difficulty in getting up after sitting for a long time; 2, when you get up in the morning, there is a feeling of back stiffness; 3, after going to sleep at night, it is difficult to turn over or wake up with pain at night; 4, lumbosacral pain or back pain improves after activity or after taking NSAIDs; 5, young people, there is acute iritis; or there is unexplained hip or knee swelling and pain; 6, there is HLA-B27 positive.