Purpura kidney is the abbreviation of allergic purpura nephritis, the full name is called allergic purpura nephritis, because allergic purpura involving the kidney also causes secondary glomerulonephritis. The clear cause is IgA immune circulating complexes, deposited in the glomeruli, capillaries and basement membrane of the kidney, resulting in increased vascular permeability and brittle changes. In addition to skin purpura, arthralgia, and abdominal pain, clinical manifestations of renal involvement can be seen. Laboratory tests can reveal positive urine protein, urine occult blood, and the presence of microscopic red blood cells and, in severe cases, carnivorous hematuria. When purpura appears, it is important to test the urine, purpura kidney, purpura invades the kidney after 4-6 weeks, need to remind the patient and the patient’s parents.