De novo myeloperoxidase-antineutrophil cytoplasmic antibody (MPO-ANCA)-associated glomerulonephritis 31 years after living-donor kidney transplantation.

A 61-year-old woman was admitted to our hospital because of an unexpected rise in serum creatinine (sCr) level with proteinuria and microhematuria. She had undergone living-donor kidney transplantation 31 years before for end-stage renal disease caused by chronic glomerulonephritis (GN). On admission, her sCr was 1.27 mg/dL which was increased from 0.6 mg/dL, urinary protein/creatinine ratio was 1.39 g/gCr, and urinary red blood cell count was more than 100 per high power field. The allograft biopsy revealed crescentic glomerulonephritis with moderate to severe tubulointerstitial inflammation. Immunofluorescence staining yielded only a minimal staining for immunoglobulin A, and negative C4d in peritubular capillary. Since increased myeloperoxidase-antineutrophil cytoplasmic antibody (MPO-ANCA) titer of 45.5 U/mL was detected, we made the diagnosis of post-transplant MPO-ANCA-associated GN. She was treated with three doses of bolus methylprednisolone (500 mg) followed by oral prednisolone therapy. Her sCr was stable at 1.20 mg/dL thereafter. ANCA-associated GN should be considered in older kidney transplant patients with new-onset urinary abnormalities because typical systemic symptoms and vasculitis in other organs might be masked by maintenance immunosuppression.