Mireille El-Ters, Umadevi Muthyala, Marie D. Philipneri, Fadi A. Hussein, Krista L. Lentine examination demonstrated blood pressure 190/105 mmHg, bibasilar rales, and bilateral lower extremity pitting edema. Initial pertinent laboratory results included blood urea nitrogen (BUN) 50 mg/dl, creatinine 7.2 mg/dl, positive ANCA by immuno- fluorescense (IF) of perinuclear or P-ANCA pattern and A B C 634 Figure 1. Biopsy specimen in the current case. (A) Light microscopy showing active necrotizing and crescentic glomerulonephritis, secondary focal and segmental glomerulosclerosis, and extensive tubular atrophy and interstitial fibrosis. (B) Immunofluorescence for IgG demonstrating granular 2+ staining along capillary walls. (C) Immunofluorescence for C3 showing granular 2-3+ deposits along capillary walls titer of 1 : 80. Myeloperoxidase antibody was positive but serine protease 3 antibody was negative. Urinalysis showed microscopic hematuria. Renal biopsy revealed active necrotizing crescentic glomerulonephritis with focal segmental glomerulosclerosis, extensive tubular atrophy and interstitial fibrosis (Figure 1A). Immu- nofluorescence demonstrated 2-3 + IgG immuno- globulin (Figure 1B) and C3 complement staining of the capillary walls (Figure 1C). The patient was placed on hemodialysis for management of volume overload and azotemia. Given the active component of necrosis and positive serum P-ANCA, he also received ten sessions of plasmapheresis, cyclophosphamide 100 mg daily, and methylprednisone 1 mg intravenously daily for three days followed by oral prednisone 1 mg/kg daily. Cyclophosphamide was reduced to 75 mg daily after 3 months and stopped at month 6. Prednisone was tapered to 15 mg daily by month three, then to 7.5 mg daily by month 6, and finally reduced by 1 mg daily every 3 to 4 weeks to discontinuation. The patient tolerated the treatment without complications, but remained hemodialysis-dependant over the year of follow-up. Discussion Anti-neutrophil cytoplasmic antibody was first reported in 1982 by Davies et al. [5] in patients with segmental necrotizing glomerulonephritis on biopsy and absent or scant, irregular deposits by direct immunoflorescence. The word “pauci” is derived from Latin which means few, and the observation of cresecentic glomerulonephritis with a paucity of IF staining for immunoglobulins led to the original definition of pauci-immune glomerulonephritis. Anti-neutrophil cytoplasmic antibody has since been described as a characteristic serological marker of small vessel vasculitides, including Wegener’s granulomatosis, microscopic polyangitis, Churg- Strauss syndrome and renal-limited vasculitis [6-8]. The pathophysiology underlying ANCA-associated crescentic glomerulonephritis classically entails the presence of auto-antibodies directed against certain cytoplasmic components of circulating neutrophils (myeloperoxidase or serine protease 3 antibodies) [9, 10]. In the glomerular tuft, antibody binding at the endothelium leads to neutrophil activation, necrotizing injury and inflammation; this also may occur in other tiny vascular beds in the body. Active inflammation is often followed by the development of fibro-cellular and fibrous crescents. The clinical course of ANCA-associated glo- merulonephritis is characterized by insidious onset of hematuria and renal insufficiency. Systemic involvement can occur and usually involves the skin, lungs, musculoskeletal, and nervous systems. Rapid decline in renal function is common, and delay in diagnosis and treatment is associated with high risk of ESRD or even death [1]. Prior to the introduction of Arch Med Sci 4, August / 2010