The disease can occur at any age, and is more common in girls aged 4 years or older, with a peak incidence in girls aged 1 to 2 years and in boys aged 2 and 9 years. According to the clinical manifestations in the first 6 months of the disease, there are 3 types. 1. The generalized type can occur at any age, with a peak incidence at 5-10 years of age and no significant gender differences. This type is characterized by an acute onset of the disease, accompanied by obvious systemic symptoms. 1.Fever Flaccid hyperthermia is the characteristic of this type. The body temperature fluctuates between 36℃ and 41℃ daily, with sudden rise and fall, and there can be 1 to 2 peaks in a day. The fever can last for weeks to months, and often recurs after natural remission. The rash is also a typical symptom of this type and has diagnostic significance. It is characterized by the appearance of fever and appears or subsides with the rise and fall of body temperature. The rash is a pale red macular rash that may fuse into patches. It can be seen anywhere on the body, but is more common on the chest and proximal extremities. 3, joint symptoms Arthritis is one of the main symptoms of the disease, the incidence is more than 80%. It can be polyarthritis or oligoarthritis. It is often aggravated by fever and reduced or relieved after the fever subsides. Knee joints are most commonly involved, and finger joints, wrists, elbows, shoulders and ankles are also frequently affected. The joints often show symmetrical swelling, pressure pain and morning stiffness, and after several years of repeated attacks, deformities may develop. The most common joint deformities are wrist ankylosis, metacarpophalangeal joint subluxation and “swan neck” deformity of the fingers. About half of the cases have enlarged liver and spleen, which may be accompanied by mild liver function abnormalities. Most children may have generalized lymph node enlargement, and abdominal pain may occur when the mesenteric lymph nodes are enlarged. Pleurisy and pericarditis About 1/3 of the children have pleurisy or pericarditis, but there are no obvious symptoms. The myocardium may also be involved, but endocarditis is rare. A small number of children have interstitial lung damage. 6. Neurological symptoms Some children have symptoms of meningeal irritation and encephalopathy, such as headache, vomiting, convulsions, increased cerebrospinal fluid pressure and electroencephalographic changes. 2.Polyarthritis type is common in girls, with 2 peak ages of onset, 1 to 3 years old and early adolescence. There are ≥5 joints involved, especially in the small joints of the fingers and toes. The onset of the disease is slow or acute, with joint stiffness, swelling and pain, and localized fever, usually with little redness. The disease usually starts in large joints, such as knees, ankles, and elbows, and gradually involves small joints, with the appearance of pachycephaly. About 1/2 of the children have involvement of the cervical joints, resulting in limited neck movement. The temporomandibular joint is involved, causing difficulty in mastication. In a few cases, cartilage and arthritis of the cricoid and arytenoid larynx occur, resulting in hoarseness and laryngeal stridor. In late stages, hip joint involvement and destruction of the femoral head may occur, resulting in impaired motion. If the joint symptoms recur and persist for several years, the joints become stiff and deformed, and the muscles near the joints atrophy. 3. Less arthritic type Usually starts at the age of 1 to 3 years, and no more than four joints are involved. The knee joint is most often involved, followed by the ankle joint, and then the small joints of the hands, but almost any joint can be involved. Iridocyclitis occurs in about 20% of children with oligoarticular JIA, and is more likely to occur in children with positive antinuclear antibodies.