Allergic purpura nephritis manifestations: The classic quadruple syndrome of allergic purpura includes skin, gastrointestinal, joint and renal involvement. I. Extra-renal symptoms 1. rash Most all patients have a rash. The rash occurs in the distal extremities, also in the buttocks and lower abdomen, mostly symmetrically distributed, as bleeding spots, above the skin surface, may be itchy, and gradually fades after 1-2 weeks. They can appear in batches. Kong Lingxin, Department of Internal Medicine, Fangshan Hospital of Traditional Chinese Medicine, Beijing, China 2. Joint symptoms Mostly occur in the ankle and knee joints, but also in the wrist and elbow joints. It is non-wandering in nature. 3. Gastrointestinal symptoms About 25%-90 patients have abdominal cramps, which can be accompanied by black stools and loose stools, and those who have had intestinal perforation or intussusception. Renal manifestations Patients with renal involvement mostly show microscopic hematuria or intermittent hematuria of the naked eye. More pediatric patients than adult patients present with hematuria. Proteinuria may also be present, and half of the patients may present with nephrotic syndrome. The long-term prognosis varies. Those with simple microscopic hematuria have a good prognosis, while those with hematuria with proteinuria (or even nephrotic syndrome) are a marker of easy combination with chronic renal impairment; however, those with nephrotic syndrome with hypertension, azotemia, and oliguria are more likely to develop end-stage renal failure.