Kidney Biopsy of a Patient With Double Positive Anti-glomerular Basement Membrane and Myeloperoxidase-Antineutrophil Cytoplasmic Antibodies

We report on an 82-year-old woman who developed rapidly progressive renal failure and whose serum creatinine level increased from 1.46 mg/dL to 7.18 mg/dL over a 3-week period.Tests for anti-glomerular basement membrane (anti-GBM) antibodies (136 U/mL) and myeloperoxidase-antineutrophil cytoplasmic antibodies (MPO-ANCA; 161 IU/mL) were both positive.Kidney biopsy revealed acute-phase lesions of necrotizing crescentic glomerulonephritis with fibrin deposition in 28 of 33 glomeruli.This finding was consistent with anti-GBM glomerulonephritis.Concentric necrotic lesions with fibrin deposition were seen from the intima to the media and extended from the interlobular arteries to the arterioles, and loss of elastic lamella continuity and extensive inflammatory cell infiltration were also observed in the surrounding areas.Tubulointerstitial nephritis with tubulitis and peritubular capillaritis was observed in the extensive areas of the tubulointerstitium.Five global sclerotic glomeruli, tubular atrophy, and interstitial fibrosis were seen.The findings were consistent with MPO-ANCApositive microscopic polyangiitis, which features a mixture of acute and chronic lesions.Hemodialysis was initiated, followed by steroid treatment.Six months later, she died and was found at autopsy to have metastatic endometrial cancer.We hypothesized that the positivity for anti-GBM antibodies and MPO-ANCA and the malignant tumor may have been related.