Ankylosing spondylitis is a chronic progressive rheumatic disease that is characterized by chronic inflammation of the spine and can also involve internal organs and other tissues. Ankylosing spondylitis also involves the sacroiliac joints, causing spinal ankylosis and fibrosis, resulting in varying degrees of eye, lung, muscle and bone lesions, and is an autoimmune disease. Most cases of ankylosing spondylitis are slow and insidious, more common in men, and generally more severe than in women. The age of onset is usually 10-40 years old, with a peak at 20-30 years old. 16 years old before the onset of the disease is called juvenile ankylosing spondylitis, and 45-50 years old after the onset of the disease is called late onset ankylosing spondylitis, and the clinical presentation is often atypical. The early symptoms of ankylosing spondylitis are insidious and may include systemic symptoms such as loss of appetite, low-grade fever, fatigue, lethargy and anemia, and in a few cases, prolonged low-grade fever and arthralgia. It is not uncommon to have acute inflammation with high fever and peripheral arthritis as the main manifestation. These cases are mostly younger and are often associated with wasting and night sweats. Inflammatory low back pain due to ankylosing spondylitis is different from mechanical low back pain and usually has the following characteristics: 1. chronic low back pain > 3 months 2. age < 40 years at the time of occurrence 3. insidious appearance, which may be accompanied by alternating hip pain 4. nocturnal pain, often waking up in the second half of the night 5. morning stiffness > 30 minutes 6. improvement with activity, not relieved by rest.