Useful biomarkers for assessment of hepatitis C virus infection-associated autoimmune disorders.

During the course of chronic hepatitis C virus (HCV) infection, various extrahepatic manifestations of autoimmune disorders may occur, including arthralgia/arthritis, sicca complex, purpura, cutaneous ulcer, and thyroid dysfunction. In addition, the prevalence of circulating autoantibodies is high among patients with HCV infection. Commonly detected autoantibodies in HCV-infected patients include rheumatoid factor, antinuclear antibody, anti-SSA/anti-SSB antibody, cryoglobulin, antineutrophil cytoplasmic antibody, anti-smooth muscle antibody, anti-liver and anti-thyroid autoantibodies. These autoantibodies may be associated with underlying autoimmune disorders or liver inflammation in HCV infection. A possible reason for antibody production is overactivation and proliferation of B lymphocytes, via the interaction with the surface protein of HCV. Because immunotherapy can cause HCV flare-up or liver damage, overdiagnosis of HCV-related autoimmune symptoms as primary autoimmune disorders should be avoided. This review describes biomarkers that are useful in clinically evaluating autoimmune manifestations and disorders associated with HCV infection.