[Extrahepatic manifestations related to hepatitis C virus].

The hepatitis C virus infects mononuclear cells and, like other viruses, can be responsible for immune disorders. The immune abnormalities described in the course of hepatitis C consist of nonspecific immunological disorders (cryoglobulinaemia, autoimmune disorders, generally associated with the presence of organ-specific or nonspecific autoantibodies). The association between mixed cryoglobulinaemia and hepatitis C has been clearly established, as 50% of patients with essential cryoglobulinaemia suffer from hepatitis C and 50% of patients with hepatitis C suffer from cryoglobulinaemia. The relationships between hepatitis C and other autoimmune disorders is less clear. The association between hepatitis C and anti-smooth muscle and antinuclear antibodies has been emphasized. However, the frequency of these autoantibodies in hepatitis C does not appear to be significantly different from than observed in other forms of viral hepatitis, especially hepatitis B. However, patients with hepatitis C have a higher incidence of anti-LKM1 antibodies than patients with other forms of viral or alcoholic liver disease. A high prevalence of hepatitis C viral infection has also been reported in Sjögren's syndrome, lichen planus and thyroid disorders. However, the relationship between viral infection and these immune disorders has not been demonstrated by large-scale epidemiological surveys or by basic virological studies. The development or exacerbation of immune disorders in patients treated by interferon has also been clearly demonstrated, which means that an autoimmune assessment, especially looking for anti-tissue and anti-thyroid antibodies, should be performed before prescribing interferon.