[A case of hepatitis C virus-associated glomerulonephropathy presenting with MPO-ANCA-positive rapidly progressive glomerulonephritis].

We report a case of hepatitis C virus-associated glomerulonephropathy presenting with MPO-ANCA-positive, rapidly progressive glomerulonephritis(RPGN). A 60-year-old woman was admitted to our hospital for evaluation of RPGN. Laboratory evaluation revealed microhematuria, proteinuria(800 mg/day), anemia, renal failure(blood urea nitrogen 27 mg/dl, serum creatinine 2.2 mg/dl), cryoglobulinemia, hypocomplementemia, positive MPO-ANCA(232 EU), and hepatitis C virus infection(GOT 58 IU/l, GPT 38IU/l, HCV-RNA(PCR) 1,200 kcopy/ml, serotype 1). After admission, the patient's renal function and anemia deteriorated rapidly, then prednisolone(30 mg/day) was started. After treatment her renal function gradually improved, then a renal and liver biopsy was performed. The renal biopsy revealed six sclerosing fibrous crescentic glomeruli in twelve glomeruli. Immunofluorescent examination revealed granular deposits of IgG, C3, and fibrinogen along the glomerular basement membrane and mesangial matrix. The pathogenesis of RPGN in this case may relate to the deposition of immune complexes in the glomeruli because immunofluorescent examination was revealed to be the immune-complex type, but not pauci immune type nephritis. Liver histology revealed chronic active hepatitis with mild piecemeal necrosis and did not reveal vasculitis. Although her renal function was improved after treatment with prednisolone, she suffered from pulmonary manifestations(dry cough etc.) on the 120th hospital day. Suddenly she died because of pulmonary hemorrhage on the 180th hospital day. These findings suggest that various HCV-induced immunological abnormalities, such as positive MPO-ANCA, cryoglobulinemia and hypocomplementemia, play an important role in the pathogenesis of this RPGN, although we could not demonstrate deposition within glomeruli of immune complexes containing HCV. The effect of interferon therapy on such immunological abnormalities remains to be documented. Since interferon is known to have immunomodulatory effects, we selected corticosteroid therapy. Future studies need to focus on the optimal treatment strategy for hepatitis C virus-associated glomerulonephritis.