A case of membranoproliferative glomerulonephritis due to type II cryoglobulinemia probably associated with hepatitis C virus infection

In recent years, several laboratories have suggested that chronic hepatitis C virus (HCV) infection is strongly associated with type II cryoglobulinemia (CG) and/or membranoproliferative glomerulonephritis (MPGN). We report here a case of MPGN due to type II CG probably associated with chronic HCV infection, and discuss the pathogenesis and treatment of such cases. A 60-year-old-female was referred to us from a local hospital because of progressive peripheral edema, purpura on the lower limbs, pleural effusion, ascites, hyperten sion, and renal failure. Laboratory findings indicated proteinuria, abnormal urinary sedi ments, normochromic normocytic anemia and azotemia. Other laboratory findings included positive rheumatoid factor, elevated serum IgM, hypocomplementemia and elevated circulat ing immune complexies. Cryoglobulin was detected and found to consist of a mixture of a monoclonal IgM κ with polyclonal IgG. Renal biopsy showed MPGN. These observations suggested a close association between MPGN and type II CG. We did not find any causes of type II CG except for positive HCV antibody and HCV RNA. Therefore, we made the diagnosis of type II CG associated with chronic HCV infection. Symptoms related to CG was responsiveness to steroid, but development of liver dysfunction developed. Treatment with alfa-interferon (α IFN) was added and thereafter, the liver dysfunction improved. However, the serum Cryo level was not reproducibly lowered. While in this case it was unclear whether IFN therapy was beneficial, several reports in addition to the findings of this case suggest a close relation between HCV infection and type II CG and MPGN. We think that performing further investigations on this condition may shed light on the more general problem of the pathogenesis and mechanisms of glomerular and vascular damage in immunologically mediated renal disease.