Membranoproliferative glomerulonephritis associated with hepatitis B and C viral infections: from viruslike particles in the cryoprecipitate to viral localization in paramesangial deposits, problematic investigations prone to artifacts.

Membranoproliferative glomerulonephritis (MPGN) is associated with hepatitis C virus infection predominantly in patients with mixed cryoglobulinemia. Viral-like particles reported in cryoglobulins and in glomerular deposits may be artifacts; in situ identification of viral genome or antigens is required to establish validity of such observations. Although the precise role for hepatitis C virus in the pathogenesis of MPGN remains to be determined, recent evidence suggests that chronic infection with hepatitis C virus may stimulate the production of the monoclonal rheumatoid factor in type II cryoglobulins that are deposited in the glomerular lesions. Interferon-alpha now appears to be the drug of choice in treating MPGN associated with hepatitis C virus infection. The association of hepatitis B virus infection with MPGN has not been convincingly established nor has its role in the pathogenesis of MPGN been demonstrated.