Allergic purpura nephritis refers to the renal damage caused by the systemic disease of allergic purpura with necrotizing small vasculitis as the main pathological change. The clinical manifestations of allergic purpura nephritis include skin purpura, joint pain, abdominal pain, blood in stool, and renal involvement mainly manifested as hematuria and proteinuria, and some severe patients may have impaired renal function. The renal involvement mostly occurs within a few days to weeks after the skin purpura. The rash of allergic purpura nephritis is characterized by hemorrhagic and symmetrical distribution in both lower limbs, ankle and knee joints, also seen in the temple and upper limbs, the rash can appear repeatedly. 2, joint symptoms: about half of the cases have wandering, multiple arthralgia, some can show joint swelling and restricted movement, often involving the knee, ankle and hand joints. No joint deformity is left behind, but recurrent attacks can occur. 3.Gastrointestinal symptoms: clinical manifestation is often abdominal pain, paroxysmal colic, in children can be complicated by intestinal overlap, intestinal obstruction and intestinal perforation. 4, other symptoms: liver, spleen, lymph node enlargement, lung bleeding resulting in hemoptysis, etc. The renal manifestations of allergic purpura nephritis 1, nephritis syndrome type: persistent microscopic hematuria, often accompanied by mild proteinuria, edema, hypertension or slowly progressive renal function impairment, this type accounts for about 10% to 15%. 2.Recurrent botrythematous hematuria: This type often appears during upper respiratory tract infection or intestinal infection, and then becomes microscopic hematuria after 2 to 3 days, and so on repeatedly. This type often appears during upper respiratory infection or intestinal infection, and then becomes microscopic hematuria. Patients usually do not have edema and hypertension, but they often have back pain, which may be unilateral or bilateral, and there is no obvious percussion pain in the kidney area on physical examination. This type is mostly seen in children and accounts for about 20% of the disease. Asymptomatic microscopic hematuria: Microscopic hematuria often persists, and the red blood cells in the urine are mainly abnormal red blood cells (more than 80%). It can be accompanied by mild proteinuria (24-hour urine protein quantification of 1g or less), which is clinically asymptomatic and mostly found during physical examination. This type is the most common, accounting for about 50%. 4, nephrotic syndrome type manifested as a large amount of proteinuria, hypoproteinemia and microscopic hematuria, accounting for about 7% to 16% of allergic purpura nephritis. If it is accompanied by hypertension and renal function damage, the prognosis is poor. 5, other types such as acute progressive nephritis syndrome, acute renal failure. About 5%. Less common clinically, poor healing. The occurrence of allergic purpura nephritis is often related to food, drugs, insect bites and other factors triggering, the discovery of abnormalities, please seek medical attention, community doctors to strengthen the publicity and education and health guidance, instructing patients to actively exercise, pay attention to prevent various triggering factors.