[A case of rapidly progressive glomerulonephritis with anti-glomerular basement membrane antibody in the course of MPO-ANCA positive interstitial pneumonia].

A 78-year-old man developed rapidly progressive glomerulonephritis (RPGN) in the course of myeloperoxidase antineutrophil cytoplasmic antibody (MPO-ANCA)-positive UIP that had been found four years previously. When UIP was diagnosed, the MPO-ANCA titer was low and urine was negative for proteinuria and hematuria. On admission, his serum creatinine increased to 16.89 mg/dL and hemoglobin decreased to 5.2 g/dL. Urinalysis revealed that urinary protein excretion was 0.423 g/day and hematuria (30-40/HPF). The MPO-ANCA titer increased to 95.6 U/mL and anti-glomerular basement membrane (GBM) antibody titer elevated to 140 EU. Renal pathology revealed cellular crescents in 10 out of 11 glomeruli excluding two global sclerotic glomeruli. Immunofluorescence showed heavy linear deposits of IgG and C3 along the GBM. Treatments were begun after admission with hemodialysis and intravenous methylprednisolone pulse therapy, oral prednisolone at the dose 30 mg/day. Both MPO-ANCA and anti-GBM antibody were within the normal range after four months. However, the renal function was not restored despite treatment and he died of pulmonary infectious disease after six months from the onset of RPGN. Recently, many cases of RPGN with both MPO-ANCA and anti-GBM antibody have been reported. In this case, persistent UIP-associated MPO-ANCA appeared to have triggered RPGN by anti-GBM antibody.