Hepatitis C virus-related cryoglobulinemia and glomerulonephritis: pathogenesis and therapeutic strategies.

Mixed cryoglobulinemia (MC) and glomerulonephritis are the most important extrahepatic manifestations of chronic hepatitis C virus (HCV) infection. MC is a non-neoplastic B cell lymphoproliferative process induced by HCV in an antigen-driven mechanism. The clinical expression of cryoglobulinemia varies from an indolent course to the development of systemic vasculitis. Glomerulonephritis is predominantly associated with MC, and almost always takes the form of membranoproliferative glomerulonephritis. The renal manifestations may range from isolated proteinuria to overt nephritic or nephrotic syndrome with variable progression towards chronic renal insufficiency. The treatment of these virus-related diseases must be individualized on the basis of the severity of clinical symptoms. Antiviral therapy with interferon alpha and ribavirin (the currently recommended treatment of HCV infection) may be successful in patients with mild-to-moderate disease, but sustained responses are uncommon. In case of severe and rapidly progressive disease, although it is capable of suppressing viremia and cryoglobulinemia, antiviral therapy is not fully effective in controlling the inflammatory and self-perpetuating reaction consequent to the deposition of cryoglobulins in the glomeruli and vessel walls. In such cases, a short course of steroids and cytotoxic drugs (with or without plasmapheresis) may be needed to improve the vascular manifestations and decrease the production of cryoglobulins. Once the acute disease flare has been controlled, antiviral therapy may be administered to eradicate HCV, the causative agent of the cryoglobulinemic syndrome. In patients in whom antiviral therapy is ineffective, contraindicated or not tolerated, rituximab, a monoclonal anti-CD20 antibody, may be an alternative to standard immunosuppression.