Rheumatoid arthritis (RA) is an autoimmune disease of unknown etiology, mostly seen in middle-aged women, with a prevalence of about 0.32-0.36% in China. The main manifestation is symmetrical, chronic, progressive polyarthritis. Chronic inflammation and hyperplasia of the synovial membrane, formation of vascular opacities, invasion of articular cartilage, subchondral bone, ligaments and tendons, resulting in destruction of articular cartilage, bone and joint capsule, eventually leading to joint deformity and loss of function. Clinical manifestations 1. Symptoms and signs There are individual differences in the condition and course of the disease, ranging from transient, mild oligoarthritis to acute progressive polyarthritis. The most commonly affected joints are the proximal interphalangeal joints, metacarpophalangeal joints, wrists, elbows, shoulders, knees and toe joints. Arthritis often presents with symmetrical, persistent swelling and pressure pain, and morning stiffness often lasts more than an hour. The most common joint deformities are ankylosis of the wrist and elbow, subluxation of the metacarpophalangeal joints, ulnar deviation of the fingers, and “swan neck” and buttonhole-like manifestations. In severe cases, the joints are fibrous or bony ankylosis, and the joint function is lost due to muscle atrophy and spasm around the joints, making life unmanageable. In addition to joint symptoms, extra-articular or visceral damage, such as rheumatoid nodules, heart, lung, kidney, peripheral nerve and eye lesions, may also occur. Most patients in the active phase have mild to moderate anemia, mostly normal white blood cell count, sometimes eosinophils and platelets are seen, serum immunoglobulin IgG, IgM, IgA can be elevated, serum complement levels are mostly normal or mildly elevated, 60% to 80% of patients have high levels of rheumatoid factor (RF), but positive RF is also seen in chronic infections (hepatitis However, RF positivity is also seen in chronic infections (hepatitis, tuberculosis, etc.), other connective tissue diseases and normal elderly people. Other autoantibodies such as anti-keratin antibodies (AKA), anti-perinuclear factor (APF) and anti-cyclic citrullinated polypeptide (CCP) have high diagnostic specificity for the diagnosis of rheumatoid arthritis, but the sensitivity is only about 30%. In order to clarify the diagnosis, stage and development of the disease, X-rays of both wrists and hands and/or feet should be taken at the beginning of the disease, as well as X-rays of other affected joints. The X-ray changes are classified as stage IV according to the degree of joint destruction Diagnostic points 1. Diagnostic criteria The diagnosis of rheumatoid arthritis mainly relies on clinical manifestations, autoantibodies and X-ray changes. Typical cases are not difficult to diagnose according to the 1987 American College of Rheumatology classification criteria, but some atypical, early rheumatoid arthritis with monoarthritis as the first symptom is often misdiagnosed or missed. For these patients, in addition to blood and urine tests, blood sedimentation, C-reactive protein, rheumatoid factor and other tests, magnetic resonance imaging (MRI) can be performed for early diagnosis. Patients with suspected rheumatoid arthritis should be regularly reviewed and closely followed up. 2.Activity judgment Items to determine the activity of rheumatoid arthritis include the severity of fatigue, duration of morning stiffness, the degree of joint pain and swelling, the number of joint pressure and swelling, the degree of restriction of joint function, and acute inflammatory indicators (such as blood sedimentation, C-reactive protein and platelets). 3, remission criteria Rheumatoid arthritis clinical remission criteria are: ① morning stiffness less than 15 minutes; ② no fatigue; ③ no arthralgia; ④ no arthralgia or no pressure pain in joints when moving; ⑤ no swelling of joints or tendon sheaths; ⑥ blood sedimentation (Weil’s method) less than 30mm/hour for women and less than 20mm/hour for men. Those who meet five or more items and for at least 2 consecutive months are considered to be in clinical remission; those with active vasculitis, pericarditis, pleurisy, myositis and recent unexplained weight loss or fever cannot be considered in remission. 4. Differential diagnosis In the diagnosis of rheumatoid arthritis, attention should be paid to differentiate it from arthritis caused by osteoarthritis, gouty arthritis, reactive arthritis, psoriatic arthritis and other connective tissue diseases (systemic lupus erythematosus, dry syndrome, scleroderma, etc.) (1) Osteoarthritis: This disease is a degenerative osteoarthropathy, with onset mostly over 40 years of age, mainly involving the knee, spine and other weight-bearing joints. The joint pain increases with activity, and there may be joint swelling and fluid accumulation. Osteoarthritis of the fingers is often misdiagnosed as rheumatoid arthritis, especially in the presence of Heberden’s nodes in the distal interphalangeal joints and Bouchard’s nodes in the proximal phalanges, which are easily treated as synovitis. X-rays show narrowing of the joint space, labyrinthine growths at the joint edges or bone warts. (2) Gout: Chronic gouty arthritis is sometimes similar to rheumatoid arthritis. Gouty arthritis is usually seen in middle-aged and elderly men, often with recurrent episodes, with the first unilateral metatarsophalangeal joint or tarsal joint as the preferred site. (3) Psoriatic arthritis: psoriatic arthritis is mainly involved in the distal joints of the fingers or toes, and joint deformities may also occur, but rheumatoid factor is negative and accompanied by psoriatic skin or nail lesions. (4) Ankylosing spondylitis: This disease mainly affects the spine, but the peripheral joints can also be involved, especially the knee, ankle and hip joints as the first symptoms, need to be distinguished from rheumatoid arthritis. The disease has the following characteristics: ① young men are more common; ② mainly invade the sacroiliac joints and spine, peripheral joint involvement is mainly asymmetric joint involvement of the lower extremities, often with tendonitis; ③ 90-95% of patients are HLA-B27 positive; ④ rheumatoid factor negative; ⑤ X-ray changes of the sacroiliac joints and spine are extremely helpful for diagnosis. (5) Arthritis due to connective tissue disease: dry syndrome and systemic lupus erythematosus can have joint symptoms, and some patients are positive for rheumatoid factor, but they have corresponding characteristic clinical manifestations and autoantibodies. (6) Other: rheumatoid arthritis with atypical single or few joints should be differentiated from infectious arthritis (including tuberculosis infection), reactive arthritis and rheumatic fever.