A case presenting with the possible relationship between myeloperoxidase-antineutrophil cytoplasmic antibody-associated glomerulonephritis and membranous changes of the glomerular basement membrane.

A 72-year-old woman exhibited elevated serum myeloperoxidase-antineutrophil cytoplasmic antibody (MPO-ANCA) levels since 2006. Her serum creatinine (sCr) levels increased from 0.5 to 1.62 mg/dl in a stepwise pattern with proteinuria and hematuria up to January 2011. Renal biopsy indicated global sclerosis (14 %), fibrocellular crescents (28 %), and Swiss cheese-like appearance of the glomerular basement membrane (GBM) on light microscopy. IgG4 staining was negative. Immunofluorescent examination indicated granular staining with IgG and C3 along the GBM. MPO-ANCA-associated glomerulonephritis with membranous nephropathy (MN) was diagnosed. As chronic changes were relatively evident in the renal biopsy specimen without acute augmentation of renal function, immunosuppressive therapy was not administered. Thereafter, rapidly progressive renal dysfunction occurred (sCr, 3.67 mg/dl in May 2011) with proteinuria (~2 g/day), hematuria, and elevated serum MPO-ANCA levels. Therefore, a second renal biopsy was performed in May 2011, indicating global sclerosis (42 %) and cellular crescents (35 %) on light microscopy. Electron microscopy indicated electron-dense deposits in the GBM and mesangial lesions. Steroid therapy was subsequently initiated, and the patient's renal function partially improved. MPO-ANCA levels decreased to within normal limits and hematuria disappeared. MPO-ANCA-associated glomerulonephritis with MN is a rare dual glomerulopathy. However, complication should be considered when urinary protein appears in large amounts. Secondary MN was suspected due to the lack of IgG4 staining and distribution of electron-dense deposits to the mesangial lesion. Renal dysfunction occurring in a stepwise pattern may be attributed to intermittent augmentation in MPO-ANCA-associated glomerulonephritis.