A 36-year-old man was admitted because of weakness, generalized edema, skin rash, and acute kidney failure with active urine sediment. Results of laboratory studies were as follows: blood leukocyte count, 14× 109/L; hemoglobin, 10 g/dL; blood platelet count, 145 × 109/L; blood urea nitrogen, 102 mg/dL; serum creatinine, 5.8 mg/dL; complement 3, 32 mg/ dL; complement 4, 3 mg/dL; serum hemolytic activity (CH50), 100 U/ mL; antinuclear antibody, 1/80; and anti-double-stranded-DNA, 1/20. On pathologic examination of the biopsy specimen from the kidney, 7 glomeruli were present, of which 1 was obsolete and others showed mesangial widening and endocapillary proliferation with neutrophilic infiltration, subendothelial hyaline deposits (wire loops), and intraluminal thrombi in some of them. Half of the glomeruli revealed cellular crescents (Figures 1 and 2). There was no spike formation. Activity index was 18/24 and chronicity index, 5/12. The fluorescent antibody technique study revealed a typically full-house pattern (Figure 3). About 40% of tubules were atrophic. Based on clinical presentation and laboratory and pathologic findings, diagnosis of diffuse proliferative lupus nephritis (class-IV-G, A/C) was established.