Cryoglobulinaemic membranoproliferative glomerulonephritis and hepatitis C virus infection.

Background/aim: A striking correlation between mixed cryoglobulinaemia and chronic hepatitis C virus infection has recently been described. Since membrano-proliferative glomerulonephritis is a rare complication of mixed cryoglobulinaemia, this study was undertaken to determine the prevalence of Hepatitis C virus infection in membrano-proliferative glomerulonephritis.

Patients: Eighteen patients, selected among a group of 121 affected by mixed cryoglobulinaemia, with renal involvement were included in the present study. A group of 148 patients affected by renal disease of different aetiology and the general population (6,917 people) were used as control groups.

Methods: The presence of anti-hepatitis C virus antibodies was determined by a commercial kit. The hepatitis C virus genotype was determined according to Okamoto. All patients underwent kidney and bone marrow biopsy, while the hepatic biopsy was performed in those showing signs of chronic liver disease.

Results: In patients with renal involvement, the kidney biopsy showed the presence of membrano-proliferative glomerulonephritis Type I in all cases. Chronic liver disease was present in eleven patients (61%). All patients were positive for serum hepatitis C virus-RNA. Bone marrow biopsy was normal in five cases, while in the others paratrabecular foci of infiltration by small lymphocytes were present. In six of these, the massive bone marrow infiltration by lymphoplas-macytoid lymphocytes suggested the diagnosis of low grade non-Hodgkin's lymphoma. In the group of patients affected by other chronic renal disease, the prevalence of hepatitis C virus infection (3.1%) was not different from that of the general population (3.2%).

Conclusions: Hepatitis C virus seems to be the aetiologic agent of mixed cryoglobulinaemia and, consequently, of membrano-proliferative glomerulonephritis.