A 16-YEAR-OLD BOY complained of puffiness of the face and legs that was especially noticable in the morning and had persisted for 2 to 3 months, as well as nausea, vomiting, a cough, and hemoptysis that had lasted for 2 to 3 days. He had had a tonsillectomy 5 years before and had been smoking nearly 30 cigarettes a day for 3 years. He was the child of first cousins. A physical examination showed a blood pressure reading of 120/80 mm Hg, a heart rate of 80/min, and a respiratory rate of 22/min. He was pale and weak and had marked edema in his eyelids and lower extremities. Decreased sounds could be heard at the base of the lungs. Laboratory investigations revealed a urinary pH of 5, a urine-specific gravity of 1015, proteinuria (4+), numerous erythrocytes, and a few leukocytes in the urine sediment. The hemoglobin level was 10.3 g/dL, and the white blood cell count was 7300/µL; all of the cells were normal on a peripheral blood smear. The erythrocyte sedimentation rate was 50 mm/h. Biochemical findings showed the following concentrations: urea, 148 mg/dL; creatinine, 4.9 mg/dL (433 µmol/L); sodium, 141 mEq/L; total protein, 3.9 g/dL; albumin, 1.8 g/dL; calcium, 7.1 mg/dL; phosphorus, 9 mg/dL (2.91 mmol/L); alkaline phosphatase, 86 U/L; triglycerides, 234 mg/dL (2.64 mmol/L); and cholesterol, 215 mg/dL (5.56 mmol/L). The creatinine clearance was 11 mL/min (0.18 mL/s)/1.73 m2. Test results were negative for antinuclear antibody and anti-DNA. Serum complement 3 (C3) and C4, serum iron and serum iron binding capacity, ferritin, prothrombin time, and partial thromboplastin time were all within normal limits. A plain chest x-ray film showed perihilar infiltration. Both of the kidneys were larger than normal with grade 2 echogenity on abdominal ultrasonography. A sputum examination was negative for hemosiderin-laden macrophages. A test for plasma anti–glomerular basement membrane (anti-GBM) antibody was positive. The kidney biopsy specimen showed glomerular epithelial crescents on light microscopy (Figure 1) and inflammatory infiltrate (Figure 2). A linear stain was seen along the GBM for IgG and C3 and to a lesser extent for IgM on an immunofluorescent examination. Treatment was started with prednisolone and furosemide. The patient's clinical condition gradually worsened with decreasing urine output, hypertension, and increasing blood urea and creatinine levels. He was given hemodialysis 3 times weekly and continued with prednisolone therapy, but unfortunately he did not respond and died.