Ankylosing spondylitis (AS) is a chronic progressive inflammatory disease that primarily affects the spine and involves the sacroiliac and peripheral joints. The disease is also known as Marie-strümpell disease, Von Bechterew disease, rheumatoid spondylitis, and rheumatoid central type, and is now called AS. Because it can also invade peripheral joints and resembles RA in its clinical, radiographic, and pathologic manifestations, it has long been viewed as a variant of rheumatoid arthritis, called rheumatoid spondylitis. In view of the absence of IgM rheumatoid factor (seronegative) in AS patients and its distinct clinical and pathologic differences from RA, the American Rheumatism Association (ARA) finally decided in 1963 to separate the two diseases, replacing “rheumatoid spondylitis” with “ankylosing spondylitis “Ankylosing spondylitis” instead of “rheumatoid spondylitis”. Symptoms and signs 1. Clinical overview The relationship between HLA-B27 and ankylosing spondylitis and spondyloarthropathies, discovered 25 years ago, has broadened our understanding of these diseases in general. These diseases start as tendon end inflammation, finger/toe inflammation or oligoarthritis, and in some cases may progress to sacroiliitis and spondylitis with or without extra-articular manifestations such as acute anterior uveitis or skin mucosal damage. Inflammation of the tendon initiation end (Figure 1) occurs in the foot (plantar fasciitis and/or heel osteochondritis and Achilles tendonitis can cause heel pain), tibial tuberosity, and other sites, while clinically significant inflammatory bowel disease, psoriasis, or infection of the intestinal or genitourinary tract is often lacking. The tendon end areas are infiltrated by lymphocytes, plasma cells, and polymorphonuclear leukocytes, and the adjacent bone marrow cavity appears edematous and infiltrated. The distinctive feature of ankylosing spondylitis is the high incidence of mid-axis myelitis and synovitis, which eventually leads to fibrosis and advanced bony ankylosis of the sacroiliac joints and spine. Although all patients with ankylosing spondylitis have varying degrees of sacroiliac joint involvement, it is uncommon to see a true complete fusion of the spine in clinical practice. Sacroiliac arthritis causes inflammatory low back pain that is insidious, difficult to localize, and felt deep in the buttocks. The pain is often unilateral and intermittent at the beginning of the disease, gradually becoming bilateral and persistent after a few months, and is also present in the lower lumbar region. Typical symptoms are prolonged fixation in a certain position or worsening upon awakening in the morning (“morning stiffness”), which can be improved by somatic activity or hot baths. Tendonitis, the main feature of spondyloarthropathies, is inflammation originating in the ligaments of the affected joint or in the area where the joint capsule attaches to the bone, near the joint ligaments, and in the synovium, cartilage, and subchondral bone. Synovitis in spondyloarthropathies is often associated with clinically undetected tendon telangiectasia, and, at least in some joints, this synovitis is only a secondary inflammatory condition. Painful extra-articular or near-articular bone pressure due to tendon end inflammation at the thoracic rib junction, sphenoid, iliac crest, sciatic tuberosity, and heel bone sites is an early feature of this type of disease. Very few patients have no or very mild low back symptoms, while others may simply complain of low back stiffness, muscle pain, and tendon tenderness. Cold or dampness may aggravate the symptoms, and this group of patients is often misdiagnosed as having fibromyalgia syndrome. Early in the disease, some patients may also present with mild systemic symptoms such as anorexia, fatigue, or low-grade fever, and these symptoms are especially common in patients with a juvenile onset of disease. Rib cartilage and rib cage, tendinitis at the transverse joint of the rib cage can cause chest pain, which is easily misdiagnosed as a result of pleurisy because it worsens with coughing or sneezing. The ratio of male to female incidence is 7:1 to 10:1. The onset of the disease is mostly in men aged 15 to 30 years old, and is rare in children and people over 40 years old. The difference in the prevalence of ankylosing spondylitis between men and women has not yet been satisfactorily explained. Occupation and pregnancy have no major impact on the disease, and the role of sex hormones is not yet certain. The clinical features of ankylosing spondylitis in women are shown in Table 1. The average age of onset in women is 26,8 years, which is 6 years later than the average age of onset in men, as reported by Peking Union Medical College Hospital. Another characteristic of ankylosing spondylitis in women is peripheral arthritis, especially the incidence of knee involvement is higher than in men, and the incidence of peripheral arthritis involvement in women was slightly higher in the analysis of 200 cases at Peking Union Medical College Hospital, 57% compared to 48%, similar to that reported by Shantou University Medical College. In addition, pubic symphysis involvement was more common in women than in men. However, the involvement of the median joint is relatively rare and mild, and thus often misdiagnosed as other rheumatic diseases. In terms of disease severity, women are generally considered to have a milder disease and a better prognosis. Attention to the differences between ankylosing spondylitis in women and men not only helps in the clinical diagnosis and differential diagnosis, but also provides useful clues for the in-depth study of the disease. Most patients have an insidious onset, with early symptoms of intermittent dull pain in the upper back, hips and hips, with stiffness or sciatica. The pain starts intermittently and is mild. As the disease progresses, it may become persistent or even more severe after several months or years. Sometimes the pain can occur higher up in the back, in and around the shoulder joint, but soon the lower back symptoms can appear. Patients often feel that the pain is worse in the morning and after a day of work, and less severe at other times. Symptoms worsen in cold and humid weather and may be relieved by salicylic acid preparations and local heat. Other patients first present with iritis of unknown origin, and the typical manifestations of ankylosing spondylitis appear years or months later, with more children than adults having this onset. Occasionally, heel pain due to palmar fasciitis or Achilles tendinitis may be an early symptom. Systemic symptoms include fatigue, malaise, anorexia, weight loss, and hypothermia. Ankylosing spondylitis is a systemic disease with both arthritic and extra-articular manifestations. 2, arthritis manifestations can involve any joint, but the spinal joints are involved more often. (1) sacroiliac arthritis most patients first appear the symptoms of sacroiliac joint involvement, individual patients may also first appear higher spinal arthritis symptoms, manifested as lower back straightening and pain, often radiating to one or both sides of the hip, and occasionally to the thigh, and can further develop to the dorsal side of the knee joint, and may even extend below the knee joint. The lower extremity extension and elevation sign is usually negative due to local inflammation of the sacroiliac joint. Pain can be induced by direct pressure on the diseased joint or by straightening the affected lower extremity. Restriction of lower back motion and mild paravertebral muscle spasm of the sacroiliac joint can occur early in the course of the disease. Pain may also be induced by finger pressure on the pubic symphysis, iliac crest, and sciatic tuberosity. The sacroiliac joint is symmetrically involved and the pubic symphysis may also be involved. The patient may be fixed in a certain position. (2) Lumbar spine arthritis: Although the sacroiliac and lumbar joints are involved at the same time, most patients have back pain and discomfort and motor dysfunction caused by lumbar spine joint lesions. The pain is diffuse in the back at first, and then gradually concentrates in the lumbar region. Severe lumbar ankylosis may sometimes occur, causing the patient to fear bending, standing upright and turning, as these movements can cause severe pain. Spinal ankylosis may be caused by spasm of the paravertebral muscles due to lumbar osteoarthritis. On examination, there may be tenderness in the lumbar osteoarthritic joints, marked spasm of the paravertebral muscles, straightening of the lumbar spine, restriction of movement, and loss of normal physiological curvature of the lumbar region. (3) Thoracic arthritis spondylitis progressive upward development, the thoracic spine joints can also be involved. In this case, the patient has upper back pain, chest pain and a sense of restricted movement of the thoracic expansion. These symptoms can occur early in the course of the disease in some patients, but most patients do not develop them until 6 years after the onset of the disease. Chest pain is usually present on inspiration. Restriction of thoracic expansion is mainly due to involvement of the cribriform joints, the sternal stalk-sternal body joints, the rib and rib cartilage joints, and the sternoclavicular joints. Thoracic expansion restriction can cause dyspnea, especially during exercise. Pulmonary function measurements are not significantly altered in most patients, as the increased amplitude of diaphragmatic motion compensates for the restricted thoracic expansion. Tenderness can be induced by finger pressure on the sternal stalk-sternal body joint, the rib and rib cartilage junction, and all thoracic vertebrae. As the disease progresses, significant kyphosis and limited thoracic movement may occur. (4) Cervical spine arthritis: A few patients may have cervical spine arthritis only as an early manifestation, and with progressive development of the disease, severe cervical spine kyphosis or lateral convexity may appear, and finally the head may be in, fixed forward flexion position, posterior flexion, rotation and lateral flexion, which may be partially or completely restricted, and the range of spatial field of vision becomes significantly smaller. Pain due to cervical spine pathology may be limited to the neck or may radiate to the head along paracervical structures, with severe spasm of the cervical musculature beginning and eventually atrophy and radicular pain involving the head and arms. Due to the ankylosis and osteoporosis of the entire spine, fractures can easily occur due to trauma, especially in the neck. Once a traumatic fracture of the neck occurs, paraplegia can result. (5) Peripheral arthritis: More than 1/3 of patients may have shoulder and hip joint involvement, which further aggravates the disabling consequences. The joint pain is often mild, but the joint movement is very limited, such as the inability to comb the hair or squatting difficulties. As the disease progresses, cartilage degeneration and fibrosis of the periarticular structures may occur, leading to joint ankylosis. Early in the course of the disease, the limitation of joint motion is mainly due to spasm of the muscles surrounding the joint. Hip contracture and compensatory flexion of the knee joint may cause the patient to be in a forward bowing and flexing position, and a duck walk may occur. Extensive lesions of the spinal joints can also cause flat chest and severe hunchback. In advanced stages of ankylosing spondylitis, the joints are painless because the inflammation has largely disappeared, and spinal fixation and ankylosis are the main manifestations. The cervical spine is fixed in an anterior tilt, the spine is kyphotic, the thorax is often fixed in an expiratory state, the lumbar spine loses its physiological curvature, the hip and knee joints are severely flexed and contracted, the eyes are fixed on the ground when standing, and the body weight is shifted forward. Individual patients may be severely disabled, bedridden for a long time and unable to take care of themselves. 3, extra-articular manifestations of ankylosing spondylitis can also appear many extra-articular manifestations, these manifestations can be primary, but most of them are secondary. In a few patients, these manifestations can occur months to years before the spondylitis. In some cases, extra-articular manifestations may overlap with other diseases, for example, aortitis, which can occur in both ankylosing spondylitis and Ritter syndrome, so ankylosing spondylitis can overlap with Ritter syndrome; heel pain is a common feature of psoriatic arthritis, Ritter syndrome, and ankylosing spondylitis, and all three patients have a high rate of HLA-B27 positivity, suggesting that these three diseases can overlap with each other. overlap. (1) Cardiac lesion autopsy revealed that about 1/4 of the patients had ascending aortic root abnormalities. However, aortic valve insufficiency due to inflammation of the aorta and aortic valve is mostly seen in patients with long duration of disease, peripheral arthritis and significant systemic symptoms (fever and anemia), so clinically only 5% of patients present with cardiac symptoms, and most patients have no conscious symptoms and only a weak diastolic tone can be heard in the second auscultatory region of the aortic valve at the left sternal border on physical examination. Occasionally, complete atrioventricular block or an episode of A-Syndrome may occur. As the disease progresses, angina pectoris may occur, and congestive heart failure may develop later in the course of the disease. In addition to aortitis, ankylosing spondylitis can be complicated by pericarditis, myocarditis and polyarteritis nodosa. (2) Pulmonary lesions: Because diaphragmatic movement can compensate for respiratory function, dyspnea rarely occurs despite restricted thoracic expansion during inspiration, and some patients may develop cough, sputum, dyspnea, and hemoptysis several years after the onset of joint symptoms. Pulmonary radiographs show dense, patchy shadows in the upper fields of both lungs, fibrosis in some patients, cavitation in others, and Aspergillus parasites. Sputum culture can be cultured with Aspergillus, which can be accompanied by mycetoma formation. In advanced patients, the thoracic expansion is limited and the lung capacity is significantly reduced. (3) Iriditis can be recurrent in about l/4 of patients and is more likely to occur the longer the course of the disease. The iritis is a non-granulomatous anterior uveitis and is usually unilateral. Ocular lesions are related to the severity and activity of the spondylitis and are most often seen in those with peripheral arthritis or a previous history of urinary tract infection, which can lead to glaucoma or blindness if left untreated. Ocular symptoms may occur before the onset of joint symptoms in individual patients. (4) Neurological lesions: Ankylosing spondylitis can cause many neurological complications, such as spontaneous atlantoaxial dislocation, which manifests as severe pain in the neck, often radiating to the temporal, occipital, or retro-orbital regions. It can also lead to vertebral collapse, vertebral fractures due to trauma, and can even cause spinal cord compression resulting in paraplegia. When the cauda equina of the spinal cord is compressed, urinary incontinence, impotence, numbness in the perineum and weakened Achilles tendon reflexes may occur. (5) Urological lesions: amyloidosis can occur in the kidneys, the incidence of which is similar to that of rheumatoid arthritis, and proteinuria can occur. A small number of patients can die from uremia. The incidence of prostatitis is also higher than that of the general population. 4. Special signs (1) Tests reflecting inflammation and injury of sacroiliac joint: for example, positive “4” test, positive sacroiliac joint separation test or positive sacroiliac joint compression test, etc. (2) Signs of restricted spinal movement: e.g. positive Schober test, restricted lateral bending, positive occipital wall test. The ability to touch the ground with the fingers when the knee is fully extended alone cannot be used to assess the mobility of the spine, because good hip function can compensate for the obvious limitation of lumbar motion, and the Schober test can more accurately reflect the degree of limitation of lumbar anterior flexion motion. Anterior lumbar convexity is progressively lost as the disease progresses. Direct pressure on the inflamed sacroiliac joint often causes pain, and sometimes sacroiliac joint pain can also be caused by compression of the iliac wings on both sides of the patient in the supine position; maximum flexion of one hip while trying to abduct the other hip; maximum flexion, abduction, and external rotation of the hip (4-character test or Patrick’s test); compression of the patient’s pelvis in the lateral position; or direct compression of the sacrum in the prone position. the sacrum in the prone position. Some patients may not have any of these signs because, on the one hand, the sacroiliac joint is surrounded by strong, firm ligaments with minimal motion and, on the other hand, in the advanced stages of the disease, the inflammation has been replaced by fibrous or bony ankylosis. (3) The difference between deep inspiration and deep expiration at the end of the flat 4th rib thorax is less than 62,5px.