Hepatitis C virus infection and membranoproliferative glomerulonephritis in Japan.

The prevalence of hepatitis C virus (HCV) infection was determined in 146 adult patients with various types of glomerulonephritis and renal diseases monitored between 1990 and 1993. Serum HCV antibody (HCV Ab) was evaluated, and positive cases were tested for HCV RNA by polymerase chain reaction. HCV infection was present in 1 (1.7%) of 58 cases of immunoglobulin A nephropathy, 0 (0%) of 14 cases of lupus nephritis, 0 (0%) of 12 cases of minimal change nephrosis, and 0 (0%) of 28 cases of other renal diseases, which is similar to the 2% prevalence observed in healthy blood donors in Japan. In contrast, HCV Ab was observed in 2 (8.3%) of 24 cases of membranous nephropathy and 6 (60%) of 10 cases of membranoproliferative glomerulonephritis (MPGN) Type I. The prevalence of HCV infection in MPGN patients was significantly higher than the frequency of HCV infection observed in the other patients with renal diseases (P < 0.001). HCV RNA was present in all cases in which HCV Ab was present. The six patients with HCV-MPGN were similar to the four patients with idiopathic MPGN with respect to age, presence of nephrotic syndrome, and renal dysfunction, but had a higher incidence of liver dysfunction, cryoglobulinemia, rheumatoid factor, and hypocomplementemia (low C3). HCV infection is present in a large percentage of patients with MPGN in Japan and clinically may differ slightly from other cases of MPGN.