General symptoms: Most patients have a history and symptoms of upper respiratory tract infection 1-2 weeks before the onset of the disease. Skin manifestations: The typical rash is a brownish-red macular rash, protruding from the skin surface, does not fade when pressed, alone or fused with each other, symmetrically distributed, more common on the extremities and buttocks, rarely invading the trunk, may be accompanied by itching or pain, appearing in batches, and may be left with pigmentation after fading. In addition to purpura, it can also be complicated by urticaria. Angioneurotic edema, erythema multiforme, or ulcerative necrosis. Occasionally, purpura may also appear on the oral mucosa or ocular conjunctiva. Joint manifestations: The joints may have mild pain to marked redness, swelling, pain and impaired mobility. The lesions often involve large joints, such as knees, ankles, elbows and wrists, and may be wandering, which is often misdiagnosed as “rheumatism”. Abdominal manifestations: abdominal pain is common, mostly in the form of colic. The pain is obvious in the umbilicus and the right lower abdomen, and may spread throughout the abdomen, but generally there is no abdominal muscle tension, and the pressure pain is light, and may be accompanied by nausea, vomiting, diarrhea and black stool. Irregular peristalsis of the intestine can lead to intussusception, and a mass can be found, mostly in children. Occasionally, intestinal perforation may occur. In the absence of skin purpura, it is often misdiagnosed as “acute abdomen”. Renal manifestations: nephritis is the most common complication of this disease, the incidence is 12-65%. It usually occurs within 1~8 weeks after the appearance of purpura and varies in severity, some are only transient hematuria, some progress to renal failure quickly, but it is rare. The main manifestations are acute glomerulonephritis such as hematuria, proteinuria, tubular urine, swelling and hypertension, etc. A few cases may become chronic nephritis, nephrotic syndrome, and individual cases may turn into chronic renal failure. The above four types (skin, joints, abdomen and kidney) can exist alone, and when two or more types are combined, they are called mixed types.