Hepatitis C virus-associated membranoproliferative glomerulonephritis in renal allografts.

In renal transplantation, chronic allograft nephropathy is the leading cause of long-term graft losses, transplant glomerulopathy being its glomerular form. Differential diagnosis from recurrent or de novo membranoproliferative glomerulonephritis should be established. Whether hepatitis C virus is associated with cryoglobulinemia and glomerular damage in renal allograft recipients, as in native kidneys, is not known. We identified six hepatitis C virus-infected renal allograft recipients with proteinuria higher than 1.5 g/day, microhematuria, and membranoproliferative glomerulonephritis. Virologic and immunologic studies were conducted. Low serum levels of circulating immune complexes and cryoglobulins were observed, which were type II immunoglobulin G polyclonal-immunoglobulin Mk monoclonal in all six patients. Classical serum complement pathway activation and at least one type of autoantibodies were present in all of them. Hepatitis C virus RNA was found in higher concentrations in cryoprecipitate than in serum (percentage of enrichment ranged from 341 to 18,200%). Hepatitis C virus genotype was 1b in 4 of 6 patients, 1a in 1 of 6 patients, and 2a in 1 of 6 patients. In renal histology prominent parietal diffuse deposition of immunoglobulin M was the rule. Glomerular subendothelial electron-dense deposits with fibrillar appearance were observed in the two patients in which electron microscopy provided information about glomeruli. In renal allograft recipients hepatitis C virus infection may be associated with type II cryoglobulinemia which may lead to membranoproliferative glomerulonephritis. Immunologic and virologic studies may help to differentiate hepatitis C virus-associated membranoproliferative glomerulonephritis from transplant glomerulopathy.