A 71-year-old man was admitted to our hospital because of fever and rapidly progressive renal insufficiency over a month. He had depression and Alzheimer's disease as complications. On admission, his serum creatinine was 5.4 mg/dL, and the serum CRP and MPO-ANCA were 18.2 mg/dL and 285 EU, respectively. A computed tomographic chest scan showed pericardiac effusion and fibrosis in both lower lung fields. Although microscopic polyangiitis(MPA)was inferred from a positive MPO-ANCA, renal biopsy could not be carried out. The initial therapy was started with pulse methylprednisolone therapy, followed by oral administration of prednisolone at the dose of 1 mg/kg(60 mg/day). As a result, his fever and inflammatory findings disappeared, and renal insufficiency was ameliorated with a smooth recovery and the pericardial effusion was markedly diminished. However, on the 18th hospital day, chest radiography revealed a nodular shadow in the right lung. Fungus infection was suspected because his serum beta-D-glucan level was extremely high (above 999 pg/mL). Mikafungin, therefore, was started at a dose of 75 mg/day and then, the dose was increased up to 300 mg/day. Nevertheless, he finally died of respiratory failure on the 26th hospital day. The autopsy findings revealed a cavity of 4.0 x 3.0 x 3.0 centimeters in size in the upper lobe of the right lung. There was a great number of fungal threads with a septal wall branched in a Y-shaped figure around the cavity, thus indicating pulmonary aspergilloma. Intranuclear inclusion bodies staining positive for cytomegalovirus were observed in all the lung fields, suggestive of a cytomegalovirus infection. In the kidney, a cellular crescent formation was noted in the majority of glomeruli showing crescentic glomeluronephritis, compatible with MPA.