A 73-year-old man with confusion, fever, and positive MPO-ANCA.

A 73-year-old man was admitted to the hospital because of progressive lethargy and fever. He had a history of hypertension since the age of 40, and was diagnosed as having a testicular tumor at the age of 50. On admission, he looked pale and stuporous. Laboratory examination revealed microscopic hematuria. The erythrocyte sedimentation rate was 110 mm/hr, and the serum CRP was 14.3 mg/dl. The titer of myeloperoxidase-antineutrophilic cytoplasmic antibodies (MPO-ANCA) was higher than 1:1000. On the sixth hospital day, he required ventilatory assistance because of aspiration pneumonia and was connected to a respirator. He was treated with intravenous corticosteroids, to which he responded in the short term with resolution of the fever and decrease in the serum CRP level, however, the consciousness disturbance persisted and the fever recurred soon thereafter. He developed gross hematuria and the renal function deteriorated. He eventually died of renal failure and pulmonary hemorrhage. Although his clinical course and laboratory findings were consistent with those of microscopic polyangitis, the pathological diagnosis was crescentic glomerulonephritis with no evidence of vasculitis.