MPO-ANCA-positive crescentic necrotizing glomerulonephritis and tubulointerstitial nephritis with renal eosinophilic infiltration and peripheral blood eosinophilia

We present the case of a 67-year-old woman with myeloperoxidase (MPO)-antineutrophil cytoplasmic antibody (ANCA)-positive pauci-immune crescentic necrotizing glomerulonephritis and tubulointerstitial nephritis with renal eosinophilic infiltration and peripheral blood eosinophilia. Staining for eosinophil cationic protein indicated that activated eosinophils were involved in the tubulitis, as well as in the glomerular injury. Marked peripheral blood eosinophilia is uncommon in ANCA-positive crescentic necrotizing glomerulonephritis associated with tubulointerstitial nephritis, except in Churg-Strauss syndrome. However, our patient had no clinical history or signs of asthma, no other signs suggestive of allergic diseases, and no histologic findings of granulomas in the kidney, thus failing to fulfill the criteria for Churg-Strauss syndrome.