Purpura nephritis is mainly caused by the allergic purpura to the kidney after the kidney damage, the main clinical manifestations are hematuria, proteinuria, some patients may even develop renal failure. Allergic purpura is mainly due to some food, drugs or unexplained allergies, allergies lead to the body IgA or IgG, which is our immune complex deposition. When it is deposited on the top of blood vessels, especially the tiny arteries and capillaries, it forms small vasculitis. When the kidneys are involved, it will affect the blood vessels of the kidneys, and generally the patients with purpura nephritis will find IgA deposits when they do kidney pathology, so this is the cause of purpura nephritis.