Post-infectious acute glomerulonephritis with vasculitis and pulmonary hemorrhage.

An 84-year-old male complained of fever, cough, sputum, and appetite loss. His renal function rapidly worsened, and he had hypoalbuminemia and hypocomplementemia. His condition worsened and C-reactive protein levels were elevated. Vasculitis syndrome was suspected and he was administered 40 mg of prednisolone, although myeloperoxidase antineutrophil cytoplasmic antibody (ANCA), proteinase-3 ANCA and antiglomerular basement membrane antibody tests were negative. His body temperature decreased and fatigue promptly resumed. On renal biopsy, light microscopy revealed endocapillary and extracapillary glomerulonephritis. Vasculitis was detected in interlobular arteries. Immunofluorescence studies revealed granular deposits of C3 and IgG along capillary walls. Electron microscopy revealed dome-shaped small electron-dense granular subepithelial deposits. Acute post-infectious glomerulonephritis was suspected. Although his renal function improved, he developed hemoptysis and was diagnosed with pulmonary hemorrhage. He received methylprednisolone and plasma exchange, and his respiratory status improved gradually. This is an extremely rare case and suggests the importance of considering a differential diagnosis.