过敏性紫癜性肾炎多见于儿童和青年,无性别差异,病因不明。其致病原可能是细菌、药物、含异体蛋白质的食物、虫咬等。基本病变为皮肤、关节和消化道的广泛性血管炎。肾损害是由于血循环中可溶性免疫复合物在肾脏内沉积导致的免疫复合物肾炎。过敏性紫癜累及肾脏者约占50%,以成年患者发生率高。一、病理主要病理改变可分为三类。(1)微小病变:在光镜下系膜细胞增生不明显,但在电镜和免疫荧光检查下可见肾小球中有广泛的IgA、IgG、C_3的沉积。(2)局灶或节段增生性:系膜和内皮细胞呈灶性增生,并有少数新月体形成,IgG、IgA、C_3、纤维蛋白原广泛沉积于肾小球中。(3)弥漫增生性:系膜、内皮细胞弥漫性增生,50%以上肾小球有新月体形成和IgG、IgA、IgM、C_3、纤维蛋白原广泛沉积。新月体超过70%以上则称为新月体肾炎。二、临床表现 Allergic purpura nephritis more common in children and young people, no gender differences, the cause is unknown. Its causative agent may be bacteria, drugs, foods containing foreign proteins, insect bites and so on. The basic lesion is the extensive vasculitis of the skin, joints and digestive tract. Renal damage is caused by immune complex nephritis caused by the deposition of soluble immune complexes in the bloodstream. Allergic purpura involving the kidneys accounted for about 50% to the high incidence of adult patients. First, the main pathological changes can be divided into three categories. (1) Micro-lesion: The mesangial cell proliferation was not obvious under the light microscope, but the deposition of IgA, IgG and C_3 in glomeruli was obvious under the electron microscope and immunofluorescence examination. (2) focal or segmental proliferative: mesangial and endothelial cells were focal hyperplasia, and a small number of crescent formation, IgG, IgA, C_3, fibrinogen widely deposited in glomeruli. (3) diffuse proliferative: mesangial, endothelial cells diffuse hyperplasia, more than 50% of glomerular crescent formation and IgG, IgA, IgM, C_3, fibrinogen widely deposited. More than 70% of the crescent is called crescentic nephritis. Second, the clinical manifestations